Server goes to sleep or crashes

I'm not sure if this is the correct place to post but have left message on ubuntu forum and am still waiting for a reply.

I
have ubuntu 10.04 LTS Server installed on a virtualbox with vbox software,
everything seems to operate as it should apart from the machine either
crashing or it goes to sleep and won't recover, it goes to black screen
and refuses to wake or respond (i'm not sure where the logs are so i can
check ?) this happens roughly every 24 hours, i have monitor software
pinging the server every 5 minutes to try keep it alive, i also have
streaming software running on the machine.

I have Airtime installed the web page displays and works fine, also the streaming
side works well but i find every morning i have to reboot to get
it all running again. Is this an Airtime issue or Ubuntu ?

Any tips or pointers would be most appreciated.