Version:            (using KDE 4.2.0)
Compiler:          gcc 4.3.3 
OS:                Linux
Installed from:    Gentoo Packages

I had KDE 4.2 installed and used the qt-copy version 4.4.9999 from gentoo's qting-edge overlay.
Everything worked fine. konqueror was stable.

I 'upgraded' qt to qt-4.5_rc1.
Afterwards I recompiled PyQt4. kdelibs, and then ALL kde-packages.
After that I rebooted.

Konqueror started to crash. A lot. If I have a konqueror window open and open one or more tabs and switch to any of them, there is a 4 in 5 chance to see konqueror crash with a segfault.

I reported this on gentoo bugzilla and got the tip to try if qt-4.5.9999 the latest qt-copy version.

I did. I installed qt-4.5.9999, rebuilt PyQt4, kdelibs, then all of kde again (including kdelibs, yes, I build it twice). After some hours of compiling I rebooted to make sure that no stale libs were left.

Result: konqueror crashes 2 out of 3 times when switching tabs.

Tracebacks and more info are to be found here:
https://bugs.gentoo.org/show_bug.cgi?id=259020