> Does anyone notice weird visual artifacts in X with recent distros?  I see it 
> in both Centos and Ubuntu.  For instance, when I alt-tab in KDE, the list of 
> windows doesn't appear, or when firefox refreshes the screen, there is a 
> noticeable delay and diagonal streaks of color like a messed up pix buffer 
> for a flash of a moment.
>
> <More details ...>
>   

I recently upgrade Fedora 6 -> Fedora 7 -> Fedora 8, and was excited to 
play with the new 3D desktop effects.  Along the way, I did something 
horrible that made all of the title bars disappear, and kinda hosed the 
environment (Gnome) in general.  A quick search resulted in:

http://linuxfud.wordpress.com/2007/02/14/how-to-reset-ubuntugnome-settings-to-defaults-without-re-installing/
http://ubuntuforums.org/showthread.php?t=419162

The short story is that there are a pile of environment settings in 
/home/<user>/.* directories.  Removing these allows you start over.  
Note that if your desktop is heavily customized, you may wish to proceed 
carefully (I had to reconfigure evolution, but wasn't a big deal) and 
"mv .<blah> .<blah>.bak" one at a time until things look better.

After doing this, I (somehow) avoided whatever I did the first time (I 
believe it was installing/fiddling with emerald); and am happy to report 
that the desktop is very well behaved with respect to screen draws.  For 
reference, I'm using kernel.x86_64.2.6.23.1-42.fc8 with 
kmod-nvidia.x86_64.100.14.19-18.lvn8 on a GEForce 6200 something or other.

I hope this helps!

Josh