Hi,
Sounds like a problem with the ATI driver's EXA implementation.
I assume
you're not using the ATI binary drivers? If not, you should probably
file a bug with X.Org bugzilla to track the problem.
This is with the open source ati driver provided by the Fedora Core X.org
implementation. Before filing a bug, I first would like to know if other people
have noticed this, just in case there's something to tweak in the xorg.conf file
to solve this. Anyway, thank you for you suggestion.
Émeric