The problem mainly manifests itself in internet browsers (Firefox, seamonkey, chrome) using various open-source drivers (ati, radeon, nv, openchrome, etc) and causes rendering problems that look like overlapping images, text, and/or menu items (see images below for examples).
I've also noticed an inability in SOHO 6 Betas where the system will not display KDE Kickoff-style menu properly, rather it just displays the outline of where the menu _should_ be. The fix below seems to have fixed this issue as well.
-as root, edit /etc/X11/xorg.conf
-in the 'Device' section, add: Option "XAANoOffscreenPixmaps" "1"
-save xorg.conf and restart X
VendorName "ATI Technologies Inc"
BoardName "Radeon Mobility"
Option "XAANoOffscreenPixmaps" "1"
Your driver, vendorname, and boardname will probably not be exactly as posted above.
This problem has plagued many folks in our community. Hopefully this solves the issues for these folks. Now we can use the most recent ff/sm releases without the annoying artifacts.