Crosspost - Kwin compositing not starting up

[el_koraco]

I posted this to ubuntuforums, then realized that I was in the wrong place. It's not about complaining, I just wanna see if I should file a bug report or not. For some unfathomable reason Kwin just went all Compiz on my Kubuntu Natty 11.04. Fresh install, x86 Emachines V140 AMD GPU, Mobility Radeon 4200, radeon driver.

Anyhoo, desktop effects got disabled out of the blue, probably after some setting I've changed, and there was no way to get them back. I'd hit enable effects in the Desktop Effects panel, whereupon I would get a notification that dekstop effects were disabled because of another function using Kwin, and asking me to hit CRTL ALT F12 to restart them. Which would get me nowhere. I tried disabling functionality checks, getting the message:

Failed to activate desktop effects using the given configuration options. Settings will be reverted to their previous values.

Check your X configuration. You may also consider changing advanced options, especially changing the compositing type.

Change the compositioning type I did, to Xrender, but when I restarted there was no way to get them back to OpenGl, lol. Running 'kwin --replace' got me this output:

OpenGL vendor string:          X.Org
OpenGL renderer string:         Gallium 0.4 on AMD RS880
OpenGL version string:         2.1 Mesa 7.10.2
OpenGL shading language version string: 1.20
Driver:                 R600G
GPU class:               R600
OpenGL version:             2.1
GLSL version:              1.20
Mesa version:              7.10.2
X server version:            1.10
Linux kernel version:          2.6.38
Direct rendering:            yes
Requires strict binding:        yes
GLSL shaders:              yes
Texture NPOT support:          yes
kwin(1806) KWin::EffectsHandlerImpl::loadEffect: EffectsHandler::loadEffect : Effect "kwin4_effect_glide" is not supported 
kwin(1806) KWin::EffectsHandlerImpl::loadEffect: EffectsHandler::loadEffect : Effect "kwin4_effect_magiclamp" is not supported 
kwin(1806) KWin::EffectsHandlerImpl::loadEffect: EffectsHandler::loadEffect : Effect "kwin4_effect_blur" is not supported 
kwin(1806) KWin::EffectsHandlerImpl::loadEffect: EffectsHandler::loadEffect : Effect "kwin4_effect_wobblywindows" is not supported 
kwin(1806) KWin::EffectsHandlerImpl::loadEffect: EffectsHandler::loadEffect : Effect "kwin4_effect_startupfeedback" is not supported , 
kwin(1806) KWin::EffectsHandlerImpl::loadEffect: EffectsHandler::loadEffect : Effect "kwin4_effect_cube" is not supported 
kwin(1806) KWin::EffectsHandlerImpl::loadEffect: EffectsHandler::loadEffect : Effect "kwin4_effect_screenshot" is not supported 
kwin(1806) KWin::EffectsHandlerImpl::loadEffect: EffectsHandler::loadEffect : Effect "kwin4_effect_cubeslide" is not supported 
kwin(1806) KWin::EffectsHandlerImpl::loadEffect: EffectsHandler::loadEffect : Effect "kwin4_effect_coverswitch" is not supported 
QInotifyFileSystemWatcherEngine::addPaths: inotify_add_watch failed: No such file or directory
QFileSystemWatcher: failed to add paths: /home/mreto/.config/ibus/bus

Now, I got the matter "sorted out", kind of, by reinstalling Kwin, and renaming my ~/.kde folder, but I wonder what this might be, and when I'll get the same kind of hassle. Anybody had these problems or might know what's going on? Should I file a bug report? I don't think this is necessarily Ubuntu related, because I've seen older threads on the OpenSuse forums complaining about the same issues.