I thought I'd fixed this last night! After leaving it plugged into the wall all day I tried booting it and it started first time but reported a memory address error. I swapped the memory module and it booted right up no probs - it was flying along. I shut it down and started it back up 5 times and it was perfect. I turned it off and packed it away. This morning I'm back to square one though! It boots to the bios loading screen and hangs and now won't power on at all. I'm going to leave it plugged in all day and see if it boots in 8 hours or so. If it does then I'm still at a loss as to what the problem is. Anyone see this behaviour before?