openSuse Clients Hang..

[tomt]

Mac OS X 10.6.8
VirtualBox 4.1.14 r77440

I have several openSuse virtual clients installed. Normally I leave them minimized or open on screen, but after a day or so they hang and become unresponsive.
When I try to interact with the GUI, I get a blank screen followed by a warning the desktop crashed and needed to be restarted.

When the desktop is restarted, nothing works, so I have to forcibly power off the virtual machine.

I've tried openSuse 11.4 and 12.1.

any one any ideas ? I don't remember having this issue with an XP host !

Thanks

[tomt]

Any one any ideas ?
This is driving me mad

[ChipMcK]

Hace you told the Guest OS to not sleep via the power management settings?