I left the computer running all day, and it went into sleep for a few hours. On wake, I was presented with the dreaded "you must restart" panic screen...

...and I'm back to square one, with OS X (both HD and USB) crashing on start up.

So it would appear that sleep is causing the panic? But why would OS X fail to start up even after a restart? I booted a linux Mint live CD without error at this point.

Is there a possibility that some data is being held in a cache or RAM even on power down and restart? That might explain why the computer started first time this morning after being off over night...

Matt