We need more info please. Please read http://techbase.kde.org/Development/Tutorials/Debugging/How_to_create_useful_crash_reports in order to improve your backtrace.

further information:
my System:
Betriebssystem:  Linux 2.6.16.27-0.9-default i686
  Aktueller Benutzer:  ludger@lr-sony-laptop
  System:  SUSE LINUX 10.1 (i586)
  KDE:  3.5.7 "release 23.1" 

The backtrace of Knetworkmanager:

Using host libthread_db library "/lib/libthread_db.so.1".
[Thread debugging using libthread_db enabled]
[New Thread -1231436112 (LWP 1963)]
[KCrash handler]
#6  0xb7789d07 in operator<< () from /usr/lib/qt3/lib/libqt-mt.so.3
#7  0xb7230cba in operator<< () from /opt/kde3/lib/libnetworkstatus.so.0
#8  0xb67994a7 in ServiceIface_stub::registerNetwork (this=0x81a88d8, 
    arg0=@0xbfd81398, arg1=@0xbfd81260) at ./src/serviceiface_stub.cpp:58
#9  0xb679a927 in Tray (this=0x8128d70) at ./src/knetworkmanager-tray.cpp:1124
#10 0xb67a838e in KNetworkManager (this=0xbfd81510)
    at ./src/knetworkmanager.cpp:91
#11 0xb67a982f in kdemain (argc=1, argv=0x807f110) at ./src/main.cpp:53
#12 0xb7232534 in kdeinitmain (argc=1, argv=0x807f110)
    at ./src/kdeinit_knetworkmanager.la.cpp:3
#13 0x0804e2ff in launch ()
#14 0x0804eb8a in handle_launcher_request ()
#15 0x0804ef0f in handle_requests ()
#16 0x0805010c in main ()

Hope this will give more information.

Valgrind Info:
==21923== Memcheck, a memory error detector.
==21923== Copyright (C) 2002-2007, and GNU GPL'd, by Julian Seward et al.
==21923== Using LibVEX rev 1732, a library for dynamic binary translation.
==21923== Copyright (C) 2004-2007, and GNU GPL'd, by OpenWorks LLP.
==21923== Using valgrind-3.2.3, a dynamic binary instrumentation framework.
==21923== Copyright (C) 2000-2007, and GNU GPL'd, by Julian Seward et al.
==21923== For more details, rerun with: -v
==21923==
==21923== My PID = 21923, parent PID = 21897.  Prog and args are:
==21923==    knetworkmanager
==21923==
==21928== Syscall param writev(vector[...]) points to uninitialised byte(s)
==21928==    at 0x417F472: do_writev (in /lib/libc-2.5.so)
==21928==    by 0x578A562: _xcb_conn_wait (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x578AAEA: _xcb_out_send (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x578AC1C: _xcb_out_flush_to (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x578C0C7: xcb_wait_for_reply (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x54194BC: _XReply (in /usr/lib/libX11.so.6.2.0)
==21928==    by 0x53FC8E1: XInternAtom (in /usr/lib/libX11.so.6.2.0)
==21928==    by 0x540FFCD: XSetWMProperties (in /usr/lib/libX11.so.6.2.0)
==21928==    by 0x4CE183E: QWidget::create(unsigned long, bool, bool) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4DA8192: QWidget::QWidget(QWidget*, char const*, unsigned) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4A1D176: KApplication::init(bool) (in /opt/kde3/lib/libkdecore.so.4.2.0)
==21928==    by 0x4A42045: KApplication::KApplication(bool, bool, KInstance*) (in /opt/kde3/lib/libkdecore.so.4.2.0)
==21928==  Address 0x57FCFC0 is 4,528 bytes inside a block of size 8,556 alloc'd
==21928==    at 0x40228F4: calloc (in /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so)
==21928==    by 0x578A760: xcb_connect_to_fd (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x578CDF8: xcb_connect (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x54186DF: _XConnectXCB (in /usr/lib/libX11.so.6.2.0)
==21928==    by 0x5401318: XOpenDisplay (in /usr/lib/libX11.so.6.2.0)
==21928==    by 0x4CAD840: qt_init_internal(int*, char**, _XDisplay*, unsigned long, unsigned long) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4CAF1BB: qt_init(int*, char**, QApplication::Type) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4D17E62: QApplication::construct(int&, char**, QApplication::Type) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4D18194: QApplication::QApplication(int&, char**, bool) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4A41E7D: KApplication::KApplication(bool, bool, KInstance*) (in /opt/kde3/lib/libkdecore.so.4.2.0)
==21928==    by 0x4A4222D: KUniqueApplication::KUniqueApplication(bool, bool, bool) (in /opt/kde3/lib/libkdecore.so.4.2.0)
==21928==    by 0x40AD0D6: KNetworkManager::KNetworkManager() (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==
==21928== Syscall param writev(vector[...]) points to uninitialised byte(s)
==21928==    at 0x417F472: do_writev (in /lib/libc-2.5.so)
==21928==    by 0x578A562: _xcb_conn_wait (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x578AAEA: _xcb_out_send (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x578B310: xcb_send_request (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x54180B5: _XPutXCBBuffer (in /usr/lib/libX11.so.6.2.0)
==21928==    by 0x54183CD: _XCBUnlockDisplay (in /usr/lib/libX11.so.6.2.0)
==21928==    by 0x52CAA2E: XRenderAddGlyphs (in /usr/lib/libXrender.so.1.3.0)
==21928==    by 0x52F1872: XftFontLoadGlyphs (in /usr/lib/libXft.so.2.1.2)
==21928==    by 0x52EE0BA: XftGlyphExtents (in /usr/lib/libXft.so.2.1.2)
==21928==    by 0x4CE9789: QFontEngineXft::stringToCMap(QChar const*, int, unsigned short*, int*, int*, bool) const (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4D2C2C4: QFontMetrics::width(QString const&, int) const (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x471DABF: KPopupTitle::calcSize() (in /opt/kde3/lib/libkdeui.so.4.2.0)
==21928==  Address 0x57FD02C is 4,636 bytes inside a block of size 8,556 alloc'd
==21928==    at 0x40228F4: calloc (in /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so)
==21928==    by 0x578A760: xcb_connect_to_fd (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x578CDF8: xcb_connect (in /usr/lib/libxcb.so.1.0.0)
==21928==    by 0x54186DF: _XConnectXCB (in /usr/lib/libX11.so.6.2.0)
==21928==    by 0x5401318: XOpenDisplay (in /usr/lib/libX11.so.6.2.0)
==21928==    by 0x4CAD840: qt_init_internal(int*, char**, _XDisplay*, unsigned long, unsigned long) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4CAF1BB: qt_init(int*, char**, QApplication::Type) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4D17E62: QApplication::construct(int&, char**, QApplication::Type) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4D18194: QApplication::QApplication(int&, char**, bool) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x4A41E7D: KApplication::KApplication(bool, bool, KInstance*) (in /opt/kde3/lib/libkdecore.so.4.2.0)
==21928==    by 0x4A4222D: KUniqueApplication::KUniqueApplication(bool, bool, bool) (in /opt/kde3/lib/libkdecore.so.4.2.0)
==21928==    by 0x40AD0D6: KNetworkManager::KNetworkManager() (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==
==21928== Invalid read of size 4
==21928==    at 0x5044A67: operator<<(QDataStream&, QString const&) (in /usr/lib/qt3/lib/libqt-mt.so.3.3.8)
==21928==    by 0x41F5C89: operator<<(QDataStream&, NetworkStatus::Properties) (in /opt/kde3/lib/libnetworkstatus.so.0.0.0)
==21928==    by 0x409E786: ServiceIface_stub::registerNetwork(QString const&, NetworkStatus::Properties) (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==    by 0x409FC5D: Tray::Tray() (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==    by 0x40AD1F6: KNetworkManager::KNetworkManager() (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==    by 0x40AD7D8: kdemain (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==    by 0x80484D1: (within /opt/kde3/bin/knetworkmanager)
==21928==    by 0x40DCF9B: (below main) (in /lib/libc-2.5.so)
==21928==  Address 0x4 is not stack'd, malloc'd or (recently) free'd
==21923== Invalid free() / delete / delete[]
==21923==    at 0x40231CF: free (in /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so)
==21923==    by 0x41C0ADD: free_mem (in /lib/libc-2.5.so)
==21923==    by 0x41C0676: __libc_freeres (in /lib/libc-2.5.so)
==21923==    by 0x401E216: _vgnU_freeres (in /usr/lib/valgrind/x86-linux/vgpreload_core.so)
==21923==    by 0x4153127: _Exit (in /lib/libc-2.5.so)
==21923==    by 0x4A282DE: KUniqueApplication::start() (in /opt/kde3/lib/libkdecore.so.4.2.0)
==21923==    by 0x40AD7BC: kdemain (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21923==    by 0x80484D1: (within /opt/kde3/bin/knetworkmanager)
==21923==    by 0x40DCF9B: (below main) (in /lib/libc-2.5.so)
==21923==  Address 0x56A6330 is not stack'd, malloc'd or (recently) free'd
==21923==
==21923== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 3 from 1)
==21923== malloc/free: in use at exit: 994 bytes in 52 blocks.
==21923== malloc/free: 3,769 allocs, 3,718 frees, 91,248 bytes allocated.
==21923== For counts of detected errors, rerun with: -v
==21923== searching for pointers to 52 not-freed blocks.
==21923== checked 631,252 bytes.
==21923==
==21923== LEAK SUMMARY:
==21923==    definitely lost: 0 bytes in 0 blocks.
==21923==      possibly lost: 0 bytes in 0 blocks.
==21923==    still reachable: 994 bytes in 52 blocks.
==21923==         suppressed: 0 bytes in 0 blocks.
==21923== Rerun with --leak-check=full to see details of leaked memory.
==21928==
==21928== Invalid free() / delete / delete[]
==21928==    at 0x40231CF: free (in /usr/lib/valgrind/x86-linux/vgpreload_memcheck.so)
==21928==    by 0x41C0ADD: free_mem (in /lib/libc-2.5.so)
==21928==    by 0x41C0676: __libc_freeres (in /lib/libc-2.5.so)
==21928==    by 0x401E216: _vgnU_freeres (in /usr/lib/valgrind/x86-linux/vgpreload_core.so)
==21928==    by 0x4153127: _Exit (in /lib/libc-2.5.so)
==21928==    by 0x4968816: KCrash::defaultCrashHandler(int) (in /opt/kde3/lib/libkdecore.so.4.2.0)
==21928==    by 0x40F0107: (within /lib/libc-2.5.so)
==21928==    by 0x41F5C89: operator<<(QDataStream&, NetworkStatus::Properties) (in /opt/kde3/lib/libnetworkstatus.so.0.0.0)
==21928==    by 0x409E786: ServiceIface_stub::registerNetwork(QString const&, NetworkStatus::Properties) (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==    by 0x409FC5D: Tray::Tray() (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==    by 0x40AD1F6: KNetworkManager::KNetworkManager() (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==    by 0x40AD7D8: kdemain (in /opt/kde3/lib/libkdeinit_knetworkmanager.so)
==21928==  Address 0x56A6330 is not stack'd, malloc'd or (recently) free'd
==21928==
==21928== ERROR SUMMARY: 8 errors from 4 contexts (suppressed: 3 from 1)
==21928== malloc/free: in use at exit: 764,490 bytes in 17,595 blocks.
==21928== malloc/free: 173,707 allocs, 156,113 frees, 12,597,621 bytes allocated.
==21928== For counts of detected errors, rerun with: -v
==21928== searching for pointers to 17,595 not-freed blocks.
==21928== checked 1,360,116 bytes.
==21928==
==21928== LEAK SUMMARY:
==21928==    definitely lost: 6,449 bytes in 182 blocks.
==21928==      possibly lost: 0 bytes in 0 blocks.
==21928==    still reachable: 758,041 bytes in 17,413 blocks.
==21928==         suppressed: 0 bytes in 0 blocks.
==21928== Rerun with --leak-check=full to see details of leaked memory.

Sorry, the Valgrind info es for Bug ID 146334 (http://bugs.kde.org/show_bug.cgi?id=146334)

Bug 146334 contains more info.

*** This bug has been marked as a duplicate of 146334 ***