I don't know about Debian. I'm using FC6 and have experiend the same problem.
I solved the problem as shown in the following link.
I hope this may help you guys.
http://groups.google.com/...3a0#e52f0b3a878073a0
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Robbie
Temporary fix
rpm -e --nodeps libX11.x86_64
http://mirror.linux.duke....0.3-6.fc6.x86_64.rpm
-- Restart your X server --