Shouldn't be a problem with a platform difference then.
Some of the very recent changes on Rawhide look like they have created some new problems for the COPY_BUFFER 0 case even in some of the versions before glcompmgr-0.4. I find that things seem to work much better in this case on xorg-x11-server-Xorg-1.1.0-13 and its predecessors than they do on the latest xorg-x11-server-Xorg-1.1.0-25.fc6. You might be better sticking to Xorg 7.0.
There is an issue with software cursors under this compositor, but it only causes minor corruption around the cursor itself. Turning to a hardware cursor eliminates this cursor problem.