Bug 213175 is related to this.
- As you can reproduce the crash at will (or you experience this regularly), can you install the "kdebase-workspace-dbg" package and post a complete backtrace here? (you can get more information at http://techbase.kde.org/User:DarioAndres/Basic_Guide_about_Crash_Reporting ) Thanks

I can't reproduce this crash.

Here it is:
Application: Systemmonitor (kdeinit4), signal: Segmentation fault
[KCrash Handler]
#6  QColor (this=0x8aad120, index=4) at /usr/include/qt4/QtGui/qcolor.h:289
#7  KSignalPlotter::beamColor (this=0x8aad120, index=4) at ../../../../libs/ksysguard/signalplotter/ksignalplotter.cpp:116
#8  0x048a8744 in FancyPlotter::answerReceived (this=0x8adbc60, id=104, answerlist=...) at ../../../ksysguard/gui/SensorDisplayLib/FancyPlotter.cc:726
#9  0x0665aac9 in KSGRD::SensorAgent::processAnswer (this=0x8a5fc40, buf=0x91a9eb0 "Free Memory\t0\t2052524\tKB\nksysguardd> ", buflen=37) at ../../../../ksysguard/gui/ksgrd/SensorAgent.cc:184
#10 0x06663acb in KSGRD::SensorShellAgent::msgRcvd (this=0x8a5fc40) at ../../../../ksysguard/gui/ksgrd/SensorShellAgent.cc:91
#11 0x06664aff in KSGRD::SensorShellAgent::qt_metacall (this=0x8a5fc40, _c=QMetaObject::InvokeMetaMethod, _id=5, _a=0xbfcb4b0c) at ./SensorShellAgent.moc:78
#12 0x0106211a in QMetaObject::metacall (object=0x8a5fc40, cl=QMetaObject::WriteProperty, idx=5, argv=0xbfcb4b0c) at kernel/qmetaobject.cpp:237
#13 0x0107089b in QMetaObject::activate (sender=0x8a46170, m=0x116f6c8, local_signal_index=5, argv=0x0) at kernel/qobject.cpp:3294
#14 0x00ff4547 in QProcess::readyReadStandardOutput (this=0x8a46170) at .moc/release-shared/moc_qprocess.cpp:162
#15 0x00ff8caf in QProcessPrivate::_q_canReadStandardOutput (this=0x8a5f958) at io/qprocess.cpp:886
#16 0x00ff9126 in QProcess::qt_metacall (this=0x8a46170, _c=QMetaObject::InvokeMetaMethod, _id=9, _a=0xbfcb4d08) at .moc/release-shared/moc_qprocess.cpp:107
#17 0x001e46fa in KProcess::qt_metacall (this=0x8a46170, _c=QMetaObject::InvokeMetaMethod, _id=17, _a=0xbfcb4d08) at ./kprocess.moc:69
#18 0x0106211a in QMetaObject::metacall (object=0x8a46170, cl=QMetaObject::WriteProperty, idx=17, argv=0xbfcb4d08) at kernel/qmetaobject.cpp:237
#19 0x0107089b in QMetaObject::activate (sender=0x8a745a0, m=0x1171550, local_signal_index=0, argv=0xbfcb4d08) at kernel/qobject.cpp:3294
#20 0x010c2053 in QSocketNotifier::activated (this=0x8a745a0, _t1=16) at .moc/release-shared/moc_qsocketnotifier.cpp:89
#21 0x01077e27 in QSocketNotifier::event (this=0x8a745a0, e=0xbfcb5124) at kernel/qsocketnotifier.cpp:317
#22 0x019ad19c in QApplicationPrivate::notify_helper (this=0x88e45d0, receiver=0x8a745a0, e=0xbfcb5124) at kernel/qapplication.cpp:4242
#23 0x019b3df7 in QApplication::notify (this=0x88baa48, receiver=0x8a745a0, e=0xbfcb5124) at kernel/qapplication.cpp:3661
#24 0x00c5a67a in KApplication::notify (this=0x88baa48, receiver=0x8a745a0, event=0xbfcb5124) at ../../kdeui/kernel/kapplication.cpp:302
#25 0x0105ceab in QCoreApplication::notifyInternal (this=0x88baa48, receiver=0x8a745a0, event=0xbfcb5124) at kernel/qcoreapplication.cpp:704
#26 0x01088faa in QCoreApplication::sendEvent (source=0x88ea898) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:215
#27 socketNotifierSourceDispatch (source=0x88ea898) at kernel/qeventdispatcher_glib.cpp:110
#28 0x011b4e88 in g_main_context_dispatch () from /lib/libglib-2.0.so.0
#29 0x011b8730 in ?? () from /lib/libglib-2.0.so.0
#30 0x011b8863 in g_main_context_iteration () from /lib/libglib-2.0.so.0
#31 0x01088bd5 in QEventDispatcherGlib::processEvents (this=0x88e45b0, flags=...) at kernel/qeventdispatcher_glib.cpp:407
#32 0x01a6ab75 in QGuiEventDispatcherGlib::processEvents (this=0x88e45b0, flags=...) at kernel/qguieventdispatcher_glib.cpp:202
#33 0x0105b4c9 in QEventLoop::processEvents (this=0xbfcb53c4, flags=) at kernel/qeventloop.cpp:149
#34 0x0105b91a in QEventLoop::exec (this=0xbfcb53c4, flags=...) at kernel/qeventloop.cpp:201
#35 0x0105fb0f in QCoreApplication::exec () at kernel/qcoreapplication.cpp:981
#36 0x019ad237 in QApplication::exec () at kernel/qapplication.cpp:3570
#37 0x048e1de7 in kdemain (argc=1, argv=0x88bd8c8) at ../../../ksysguard/gui/ksysguard.cc:582
#38 0x0804dff7 in launch (argc=<value optimized out>, _name=<value optimized out>, args=<value optimized out>, cwd=0x0, envc=1, envs=0x88bdbab "DISPLAY=:0.0", reset_env=false, tty=0x0, 
    avoid_loops=false, startup_id_str=0x88bdbbc "penguin;1264160370;587068;6473_TIME10130304") at ../../kinit/kinit.cpp:706
#39 0x0804ec15 in handle_launcher_request (sock=<value optimized out>, who=<value optimized out>) at ../../kinit/kinit.cpp:1198
#40 0x0804f08c in handle_requests (waitForPid=<value optimized out>) at ../../kinit/kinit.cpp:1391
#41 0x0804fe27 in main (argc=4, argv=0xbfcb5ef4, envp=0xbfcb5f08) at ../../kinit/kinit.cpp:1830

Do you have any devices plugged in? E.g. mobile phone etc.

There's a related crash when you have a mount point with \n in its name.

No. But there is a second internal harddrive with different partitions mounted. One of them is called /windows/ which is with an an n without an \ in its name.

Created attachment 41594 [details]
New crash information added by DrKonqi

System monitor crashed when I pulled k8 cpu sensor into the hdd graph.

*** Bug 229061 has been marked as a duplicate of this bug. ***

*** Bug 230155 has been marked as a duplicate of this bug. ***

*** Bug 238386 has been marked as a duplicate of this bug. ***

*** Bug 238621 has been marked as a duplicate of this bug. ***

*** Bug 244170 has been marked as a duplicate of this bug. ***

Created attachment 51507 [details]
New crash information added by DrKonqi

ksysguard (4.5.1 (KDE 4.5.1)) on KDE Platform 4.5.1 (KDE 4.5.1) using Qt 4.7.0

- What I was doing when the application crashed:

Pulled cpu temperature sensor into diagram and program crashed.

-- Backtrace (Reduced):
#6  QColor (this=0x2640070, index=<value optimized out>) at /usr/include/qt4/QtGui/qcolor.h:292
#7  KSignalPlotter::beamColor (this=0x2640070, index=<value optimized out>) at ../../../../libs/ksysguard/signalplotter/ksignalplotter.cpp:109
#8  0x00007fc286e68457 in FancyPlotter::answerReceived (this=0x255a6e0, id=<value optimized out>, answerlist=<value optimized out>) at ../../../ksysguard/gui/SensorDisplayLib/FancyPlotter.cc:712
#9  0x00007fc285f77c5e in KSGRD::SensorAgent::processAnswer (this=0x24efd10, buf=<value optimized out>, buflen=<value optimized out>) at ../../../../ksysguard/gui/ksgrd/SensorAgent.cc:184
#10 0x00007fc285f7f6be in KSGRD::SensorShellAgent::msgRcvd (this=0x24efd10) at ../../../../ksysguard/gui/ksgrd/SensorShellAgent.cc:91

*** Bug 242625 has been marked as a duplicate of this bug. ***

Created attachment 54041 [details]
New crash information added by DrKonqi

ksysguard (4.5.4 (KDE 4.5.4)) on KDE Platform 4.5.4 (KDE 4.5.4) using Qt 4.7.0

- What I was doing when the application crashed:

tried to add a sensor it8712
All other sensors are added correctly

-- Backtrace (Reduced):
#6  QColor (this=0x270f5e0, index=<value optimized out>) at /usr/include/qt4/QtGui/qcolor.h:292
#7  KSignalPlotter::beamColor (this=0x270f5e0, index=<value optimized out>) at ../../../../libs/ksysguard/signalplotter/ksignalplotter.cpp:109
#8  0x00007f216dccb3c7 in FancyPlotter::answerReceived (this=0x28a4f60, id=<value optimized out>, answerlist=<value optimized out>) at ../../../ksysguard/gui/SensorDisplayLib/FancyPlotter.cc:712
#9  0x00007f216cde874e in KSGRD::SensorAgent::processAnswer (this=0x2721030, buf=<value optimized out>, buflen=<value optimized out>) at ../../../../ksysguard/gui/ksgrd/SensorAgent.cc:184
#10 0x00007f216cdf01ae in KSGRD::SensorShellAgent::msgRcvd (this=0x2721030) at ../../../../ksysguard/gui/ksgrd/SensorShellAgent.cc:91

Created attachment 57004 [details]
New crash information added by DrKonqi

ksysguard (4.6.00 (4.6.0) "release 381") on KDE Platform 4.6.00 (4.6.0) "release 381" using Qt 4.7.1

- What I was doing when the application crashed:

dragged CPU clock frequency onto HD sensor.

-- Backtrace (Reduced):
#6  QColor (this=<value optimized out>, index=<value optimized out>) at /usr/include/QtGui/qcolor.h:292
#7  KSignalPlotter::beamColor (this=<value optimized out>, index=<value optimized out>) at /usr/src/debug/kdebase-workspace-4.6.0/libs/ksysguard/signalplotter/ksignalplotter.cpp:109
#8  0x00007fb9b017e51a in FancyPlotter::answerReceived (this=0x84e940, id=110, answerlist=<value optimized out>)
    at /usr/src/debug/kdebase-workspace-4.6.0/ksysguard/gui/SensorDisplayLib/FancyPlotter.cc:712
#9  0x00007fb9afa96018 in KSGRD::SensorAgent::processAnswer (this=0x7eed60, buf=<value optimized out>, buflen=<value optimized out>)
    at /usr/src/debug/kdebase-workspace-4.6.0/ksysguard/gui/ksgrd/SensorAgent.cc:184
#10 0x00007fb9afa9d0fe in KSGRD::SensorShellAgent::msgRcvd (this=<value optimized out>) at /usr/src/debug/kdebase-workspace-4.6.0/ksysguard/gui/ksgrd/SensorShellAgent.cc:91

Let me rephrase: dragged CPU clock frequency onto HD totals tab.

This is probably due to the fact one is a float and the other one is an integer.

[Comment from a bug triager]
From bug 263536 (KDE SC 4.4.5):
-- Information about the crash:
When adding additional fields to Hard Disk Totals (such as the I/Os currently
in progress under Disk Throughput -> sda -> I/Os currently in progress), KDE's
System Monitor rolls over and dies.

From bug 263819 (KDE SC 4.4.5):
-- Information about the crash:
Different things happen depending on the section of Sensor Browser under which
the sensor being added is found.

Crashes:
System > Processors, Cores
CPU Load
Hardware Sensors
Partition Usage (some, sometimes)
Disk Throughput > sd*
Memory > swap
Network

Doesn't crash, doesn't add to graph:
logfiles
Partition Usage (some, sometimes)

Doesn't crash, adds to graph:
System > Uptime
Partition Usage > System Load
Disk Throughput > ram
Memory > physical
Process Count

What happens for a given item under Partition Usage varies. One that gets added
one time can crash it the next. It seems like it might partially depend on the
order in which multiple things are added.
The crash can be reproduced every time.

From bug 263819 comment 2 (KDE SC 4.6.0):
- What I was doing when the application crashed:
Tried to drag CPU sensors to the graph.
- Custom settings of the application:
Installed Hard Disk Tab

*** Bug 267991 has been marked as a duplicate of this bug. ***

*** Bug 263819 has been marked as a duplicate of this bug. ***

*** Bug 263536 has been marked as a duplicate of this bug. ***

Created attachment 57949 [details]
New crash information added by DrKonqi

ksysguard (4.5.1 (KDE 4.5.1)) on KDE Platform 4.5.1 (KDE 4.5.1) using Qt 4.7.0

- What I was doing when the application crashed: I also crashed System Monitor by dragging a sensor

-- Backtrace (Reduced):
#6  QColor (this=0x2616ae0, index=<value optimized out>) at /usr/include/qt4/QtGui/qcolor.h:292
#7  KSignalPlotter::beamColor (this=0x2616ae0, index=<value optimized out>) at ../../../../libs/ksysguard/signalplotter/ksignalplotter.cpp:109
#8  0x00007f04b3d093c7 in FancyPlotter::answerReceived (this=0x2616950, id=<value optimized out>, answerlist=<value optimized out>) at ../../../ksysguard/gui/SensorDisplayLib/FancyPlotter.cc:712
#9  0x00007f04b2e2874e in KSGRD::SensorAgent::processAnswer (this=0x24625f0, buf=<value optimized out>, buflen=<value optimized out>) at ../../../../ksysguard/gui/ksgrd/SensorAgent.cc:184
#10 0x00007f04b2e301ae in KSGRD::SensorShellAgent::msgRcvd (this=0x24625f0) at ../../../../ksysguard/gui/ksgrd/SensorShellAgent.cc:91

Git commit 68fc9687b99ad04598d037f4bf3bb23a15c0ffef by John Tapsell.
Committed on 14/03/2011 at 11:21.
Pushed by johnflux into branch 'KDE/4.6'.

Fix crash when mixing summation and non-summation sensors

Also fix the tooltip to make it look better when mixing summation and
non-summation sensors

BUG:223095

M  +16   -4    ksysguard/gui/SensorDisplayLib/FancyPlotter.cc     

http://commits.kde.org/kde-workspace/68fc9687b99ad04598d037f4bf3bb23a15c0ffef

Git commit fa2ae6b6c3f4563d7af9e7ab94f6faf68ab7304e by John Tapsell.
Committed on 14/03/2011 at 11:21.
Pushed by johnflux into branch 'master'.

Fix crash when mixing summation and non-summation sensors

Also fix the tooltip to make it look better when mixing summation and
non-summation sensors

BUG:223095

M  +16   -4    ksysguard/gui/SensorDisplayLib/FancyPlotter.cc     

http://commits.kde.org/kde-workspace/fa2ae6b6c3f4563d7af9e7ab94f6faf68ab7304e

Git commit d819fde3d2a1c1e28008da39f174b3959863f370 by John Tapsell.
Committed on 14/03/2011 at 11:21.
Pushed by johnflux into branch 'KDE/4.5'.

Fix crash when mixing summation and non-summation sensors

Also fix the tooltip to make it look better when mixing summation and
non-summation sensors

BUG:223095

M  +16   -4    ksysguard/gui/SensorDisplayLib/FancyPlotter.cc     

http://commits.kde.org/kde-workspace/d819fde3d2a1c1e28008da39f174b3959863f370

Thank you very much for all those that reported this, and to Dario especially for putting all the bug reports together.

You're welcome!. Thanks for the fix :)

*** Bug 261935 has been marked as a duplicate of this bug. ***

*** Bug 263819 has been marked as a duplicate of this bug. ***