I have the same problem with the nvidia beta drivers.
I'm using debian unstable with the nvidia beta driver from experimental and with the beryl packages from http://forum.debian-fr.org/viewtopic.php?t=4985
(sorry it's a french forum)
But wenn i start beryl with the option beryl --force-aiglx && beryl-manager
it works fine for me ! Hope this can help you.
The only problem is that i'm unable to read video with mplayer ot totem because the video output doesn't work anymore, but it's very nice to see beryl running on my machine.