Version:           3.0.0 (using KDE KDE 3.0.3)
Installed from:    Compiled From Sources
Compiler:          g++ 2.95.3 
OS:          Linux

I can reproduce the crash. 
Opening more than one source files, NOT in a project, some file had the lines not correctly indented. I moved on one of this line and press tab to reindent correctly the line/s but the curson disappered and after some seconds, the application crashs with sig 6.
The indent style was set in the preferences to ANSI

All default plugins loaded exept "File Selector"

Backtrace follows:

0x41486239 in wait4 () from /lib/libc.so.6
#0  0x41486239 in wait4 () from /lib/libc.so.6
#1  0x41500e58 in __check_rhosts_file () from /lib/libc.so.6
#2  0x4133b7b2 in waitpid () from /lib/libpthread.so.0
#3  0x408bf63f in KCrash::defaultCrashHandler ()
   from /opt/kde//lib/libkdecore.so.4
#4  0x41339144 in pthread_kill () from /lib/libpthread.so.0
#5  0x4140d288 in sigaction () from /lib/libc.so.6
#6  0x41339531 in raise () from /lib/libpthread.so.0
#7  0x4140e88b in abort () from /lib/libc.so.6
#8  0x413a8f28 in __terminate () at ../../gcc-2.95.3/gcc/libgcc2.c:-1
#9  0x413a8f45 in __terminate () from /usr/lib/libstdc++-libc6.2-2.so.3
#10 0x413a9940 in throw_helper (eh=0x53f00478, pc=0x432d7b12, 
    my_udata=0xbfffefac, offset_p=0xbfffefa8)
   from /usr/lib/libstdc++-libc6.2-2.so.3
#11 0x413a9af5 in __throw () from /usr/lib/libstdc++-libc6.2-2.so.3
#12 0x413ab836 in __builtin_vec_new (sz=536870912)
    at ../../gcc-2.95.3/gcc/cp/new2.cc:39
#13 0x40f1464a in QString::setLength () from /usr/local/qt/lib/libqt-mt.so.3
#14 0x40f1a1a4 in QString::operator+= () from /usr/local/qt/lib/libqt-mt.so.3
#15 0x432d7b13 in indentLine () from /opt/kde/lib/kde3/libqeditorpart.so
#16 0x432d7e74 in CIndent::indent () from /opt/kde/lib/kde3/libqeditorpart.so
#17 0x40ca75bd in QTextParagraph::indent ()
   from /usr/local/qt/lib/libqt-mt.so.3
#18 0x40c8a6f7 in QTextCursor::indent () from /usr/local/qt/lib/libqt-mt.so.3
#19 0x40d8c796 in QTextEdit::indent () from /usr/local/qt/lib/libqt-mt.so.3
#20 0x432e5082 in QEditor::keyPressEvent ()
   from /opt/kde/lib/kde3/libqeditorpart.so
#21 0x40c789b0 in QWidget::event () from /usr/local/qt/lib/libqt-mt.so.3
#22 0x40d84182 in QTextEdit::event () from /usr/local/qt/lib/libqt-mt.so.3
#23 0x432e666b in QEditor::event () from /opt/kde/lib/kde3/libqeditorpart.so
#24 0x40be06fe in QApplication::internalNotify ()
   from /usr/local/qt/lib/libqt-mt.so.3
#25 0x40bdfde0 in QApplication::notify () from /usr/local/qt/lib/libqt-mt.so.3
#26 0x40848a64 in KApplication::notify () from /opt/kde//lib/libkdecore.so.4
#27 0x40b7f8e7 in QETWidget::translateKeyEvent ()
   from /usr/local/qt/lib/libqt-mt.so.3
#28 0x40b7a6b7 in QApplication::x11ProcessEvent ()
   from /usr/local/qt/lib/libqt-mt.so.3
#29 0x40b7987b in QApplication::processNextEvent ()
   from /usr/local/qt/lib/libqt-mt.so.3
#30 0x40be221f in QApplication::enter_loop ()
   from /usr/local/qt/lib/libqt-mt.so.3
#31 0x40b797eb in QApplication::exec () from /usr/local/qt/lib/libqt-mt.so.3
#32 0x0805f35e in main ()
#33 0x413fc17d in __libc_start_main () from /lib/libc.so.6