Suspend Problem

[rh]

I am using Ubuntu 64 bit on an AMD 64 Desktop box. Usually I switch to
suspend to RAM mode while the PC is not in use. This worked properly
until Ubuntu 11.04. Now returning from suspend works only every second
time. And every second time the screen stays black after the login.
Before the login screen appears i see the screensaver in those cases
which afterwards are successful. If there is no screensaver the return
from suspend does not work.

Any suggestions?

-- 
Reinhard