Ubuntu crashing

Hi

I am running ubuntu on Vmware, when i log in, the desktop background starts to crash, but the weird thing is that i can run other programs, such as the konsole without any crash.

I have a Intel(R) core i3 CPU 2.40 Ghz
Installed ram 4.00 GB (3.80 usable)

i run windows 7.

what could the problem be ?

Thanks.