I have the exact same issue, i have a radeon 9600XT, on amd64, using EXA, composite, and glx. I am unstable up-to-date. and I user konqueror, no 3D effects or transparency at all (no beryl nor compiz). reading a similar issue in ubuntu, I tried to install libx11-1.1.1 instead of libx11-1.0.3, but it didn't change anything. I am using the "radeon" driver, not fglrx. I have no clue at what is going on ...