KDE4 compositing won't switch on

[Donn]

Kubuntu Jaunty - 64bit
KDE 4.2.x
Nvidia card using nvidia-glx-180

Suddenly I can't enable desktop effects. The screen goes wild and comes and 
goes (from that login wallpaper with the fuzzy dots). It then reports that 
kwin has crashed... but the effects don't get enabled. Last week I could use 
them fine. I had a spell in Gnome* again (trying to get past the general horror 
of Jaunty ) but that's all.

Any tips? I checked .xsession-errors and it only says stuff like:

X Error: BadWindow (invalid Window parameter) 3
  Major opcode: 20 (X_GetProperty)
  Resource id:  0x8e00081
Application::crashHandler() called with signal 11; recent crashes: 2
KCrash: Application 'kwin' crashing...
kdeinit4: preparing to launch /usr/lib/kde4/libexec/drkonqi

Which is as illuminating as a power-outage...

Halp!

\d

*Gnome which is, BTW, not much better than KDE4. It's also crashy and fragile.
\o/ KDE4 is not alone :)

-- 
home: http://otherwise.relics.co.za/
2D vector animation : https://savannah.nongnu.org/projects/things/
Font manager : https://savannah.nongnu.org/projects/fontypython/