Blank screen after logout Ubuntu 13.04

I have recently installed Ubuntu 13.04 x64 on a 2013 UEFI laptop which was running Win8. Now I only have Ubuntu 13.04.

The distribution is working well in most case. However, a few seconds after I logout, I see a blank screen. After a few seconds, I can hear the dum-dum sound. If I press on my Num Lk key or CapsLk, the light indicator still works.

I cannot suspend either.

I suspect it is a display error, since my laptop has only the 1600x900 res.

Thank you.

Here are some of my specs:
Processor 2x Intel(R) Pentium(R) CPU 2020M @ 2.40GHz

Memory 3914MB (1554MB used)

Operating System Ubuntu 13.04