I have only started seeing this problem recently. I recently upgraded my computer, and installed one new video card in it (I have 3 currently running), but I am not sure if this is really an issue with my hardware or VirtualBox. I have searched the forums and found some similar problems reported by other people, although no obvious solution.
I am running VB 4.1.20, and I have a few WinXP guest VMs running on my host machine, which is running Win 7 64-bit. From time to time, the screens stop updating information. Furthermore, I can't manipulate anything on the screen, clicking doesn't select anything in the VM, and it appears to be frozen.
However, when I minimize and then maximize again, everything comes back up. Previously I had 2 CPUs allocated for each VM, now it's just 1 (and it's still happening). I have 2D acceleration turned on, not 3D. Max video RAM (128MB) allocated for each VM, and sounds enabled. (I say all of this because i've read some suggestions that said to try changing these parameters.)
The problem is still happening. Is this a known issue, and if so, is there a fix for it?
(Also, why is the max video ram only 128 MB? Some of us have a lot more memory on our machines, it would be nice to be allocate more video RAM than that...)
EDIT: One thing to possibly note: I have 2 ATI cards and one Nvidia card in my system, driving a total of 8 monitors. It is possible that the VMs are spanning 2 monitors where one monitor is one of the ATI cards, and the other one is the NVidia card. I could see how that might be a problem, since there are two different drivers for the two different monitors spanning the same VM. Could this be causing it, if that is the case? (I still have to check if this is actually the way it's set up...)