Vista Aero Windows Minimization Animation Strangeness

I have noticed that my Windows Vista machine gets into a mode such that when
I minimize a window it gets pushed back to the back of the other windows
and then minimizes. The pretty animation is there but since it is behind the
other windows I don't see the whole effect.

Sometimes I can get this to work properly by logging out but not always.

Any idea how to fix this?

I am running Windows Vista Ultimate on a Dell Inspiron 640m, 2 GB RAM and
Intel Mobile Intel(R) 945GM Express Chipset Family.

Thanks,

Mike