It also happens to me, using Archlinux and Calligra Sheets 2.8.7. It always crashes when I try to open the default template. Calligra Words works just fine.

Confirmed on Arch Linux x86_64 with latest Calligra Sheets 2.9.0.

Backtrace with debugging symbols from breeze:

Application: Calligra Sheets (calligrasheets), signal: Segmentation fault
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[KCrash Handler]
#6  QWidget::mapFromParent (this=this@entry=0x0, pos=...) at kernel/qwidget.cpp:4325
#7  0x00007fe2a4adfb03 in QWidget::mapFrom (this=<optimized out>, parent=0x2dfd680, pos=...) at kernel/qwidget.cpp:4292
#8  0x00007fe295d4e0b2 in Breeze::Style::eventFilterScrollArea (this=0x0, widget=0x2dfd680, event=0x7fff84ac8d10) at ../../kstyle/breezestyle.cpp:1025
#9  0x00007fe2a4093776 in QCoreApplicationPrivate::sendThroughObjectEventFilters (this=this@entry=0x2429ce0, receiver=receiver@entry=0x2dfd680, event=event@entry=0x7fff84ac8d10) at kernel/qcoreapplication.cpp:1065
#10 0x00007fe2a4a9f99c in QApplicationPrivate::notify_helper (this=this@entry=0x2429ce0, receiver=receiver@entry=0x2dfd680, e=e@entry=0x7fff84ac8d10) at kernel/qapplication.cpp:4566
#11 0x00007fe2a4aa663f in QApplication::notify (this=<optimized out>, receiver=receiver@entry=0x2c14110, e=e@entry=0x7fff84ac8ff0) at kernel/qapplication.cpp:4113
#12 0x00007fe2a561afe7 in KoApplication::notify (this=<optimized out>, receiver=0x2c14110, event=0x7fff84ac8ff0) at /mnt/ubuntu/calligra/calligra-2.9.0/libs/main/KoApplication.cpp:623
#13 0x00007fe2a409360d in QCoreApplication::notifyInternal (this=0x7fff84ac9870, receiver=receiver@entry=0x2c14110, event=event@entry=0x7fff84ac8ff0) at kernel/qcoreapplication.cpp:955
#14 0x00007fe2a4aa5c9f in sendEvent (event=<optimized out>, receiver=<optimized out>) at ../../include/QtCore/../../src/corelib/kernel/qcoreapplication.h:231
#15 QApplicationPrivate::sendMouseEvent (receiver=receiver@entry=0x2c14110, event=event@entry=0x7fff84ac8ff0, alienWidget=alienWidget@entry=0x2c14110, nativeWidget=nativeWidget@entry=0x2dfd680, buttonDown=buttonDown@entry=0x7fe2a55cb578 <qt_button_down>, lastMouseReceiver=..., spontaneous=true) at kernel/qapplication.cpp:3178
#16 0x00007fe2a4b1f9d2 in QETWidget::translateMouseEvent (this=this@entry=0x2dfd680, event=event@entry=0x7fff84ac9220) at kernel/qapplication_x11.cpp:4632
#17 0x00007fe2a4b1e84a in QApplication::x11ProcessEvent (this=0x7fff84ac9870, event=event@entry=0x7fff84ac9350) at kernel/qapplication_x11.cpp:3827
#18 0x00007fe2a4b47bc2 in x11EventSourceDispatch (s=0x242b530, callback=0x0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
#19 0x00007fe2a0959c3d in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#20 0x00007fe2a0959f20 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#21 0x00007fe2a0959fcc in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0
#22 0x00007fe2a40c2c7e in QEventDispatcherGlib::processEvents (this=0x2429ca0, flags=...) at kernel/qeventdispatcher_glib.cpp:450
#23 0x00007fe2a4b47c86 in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
#24 0x00007fe2a4092161 in QEventLoop::processEvents (this=this@entry=0x7fff84ac9730, flags=...) at kernel/qeventloop.cpp:149
#25 0x00007fe2a40924c5 in QEventLoop::exec (this=this@entry=0x7fff84ac9730, flags=...) at kernel/qeventloop.cpp:204
#26 0x00007fe2a4097f49 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1227
#27 0x00007fe2a4a9dc1c in QApplication::exec () at kernel/qapplication.cpp:3828
#28 0x00007fe2a5c99762 in kdemain (argc=1, argv=0x7fff84ac99b8) at /mnt/ubuntu/calligra/calligra-2.9.0/sheets/part/Main.cpp:44
#29 0x00007fe2a58f3ec5 in __libc_start_main (main=0x4006e0 <main(int, char**)>, argc=1, argv=0x7fff84ac99b8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff84ac99a8) at libc-start.c:287
#30 0x000000000040070e in _start ()

Confirmed on Kubuntu with Plasma 5.2.1 and Calligra 2.9.0

This looks like a breeze issue, re-assigning. From investigating, it looks like breeze's eventFilterScrollArea attempts to access scrollbars on QAbstractScrollArea-derived widgets, even if these scrollbars do not exist (sheets calls setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);).

Interesting. The code do check for the scrollbar validity (non nullptr) few lines above the one incriminated. I guess I'll check for scrollbar policy directly.

Git commit 759ff9bf1ba38a47214849bc0a80cfbc7333c3a9 by Hugo Pereira Da Costa.
Committed on 01/03/2015 at 17:19.
Pushed by hpereiradacosta into branch 'Plasma/5.2'.

Check scrollbar policy before forwarding events

M  +3    -3    kstyle/breezestyle.cpp

http://commits.kde.org/breeze/759ff9bf1ba38a47214849bc0a80cfbc7333c3a9

Git commit e5830632fc7fea9382efa640338ede7178a674f3 by Hugo Pereira Da Costa.
Committed on 01/03/2015 at 17:19.
Pushed by hpereiradacosta into branch 'master'.

Check scrollbar policy before forwarding events

M  +8    -7    kstyle/breezestyle.cpp

http://commits.kde.org/breeze/e5830632fc7fea9382efa640338ede7178a674f3

Fixed.
Thanks for reporting (and forwarding)

*** Bug 344808 has been marked as a duplicate of this bug. ***

*** Bug 344310 has been marked as a duplicate of this bug. ***

*** Bug 345040 has been marked as a duplicate of this bug. ***

*** Bug 345616 has been marked as a duplicate of this bug. ***