Version:            (using KDE 4.2.0)
Compiler:          4.3.2 kde 4.2 downloaded from the experimental kubuntu repository
OS:                Linux
Installed from:    Ubuntu Packages

1. just installed kde 4.2 from kubuntu repository.
   Running ubuntu 8.10 ibex interpid.
2. gdm is the display manager (through which I login).
3. kde is my default desktop manager - to which I normally sign in.
4. After I updated to 4.2.0 - couldn't finish the login - until the hack 
   below.
5. problem:
   Splash screen appears, shows the 1st icon, then freezes.
   After several minutes, crash from kbuildsyscoca4 on SIGABRT.
   could do anything by close (save as hanged completely).

6. Once I closed, several more kbuildsyscoca4 similar crashes appeared.
7. Then the old desktop was shown (before kde 4), but no task bar.
8. <alt>+<tab> or any other keyboard shortcut didn't work - had to switch 
   windows by dragging and selecting with mouse.
9. google: 
    found several old mentioning of kbuildsyscoca4, with relation 
    to the various errors reported in $HOME/.xsession-errors.
    (e.g., "/usr/bin/xmodmap:  unable to open file '/usr/share/apps/kxkb/ubuntu.xmodmap' for reading"
    kbuildsycoca4(7079) KConfigGroup::readXdgListEntry: List entry MimeType in "ServiceMenus/preview.desktop" is not compliant with XDG standard (missing trailing semicolon).
     etc.)

10. But - I didn't know whether this was the problem or not.


11. So the hack:
    I deleted $HOME/.local folder (well - saved it in a different name).
    Then it did survive the login - and I am now able to respond to you.

If you wish for more information, please do not hesitate to email.
I only wish I could spend time to study kde and debug this myself...

Thanx (for the wonderful job!) and best regards,
Jigal.