BSOD Driver_Power_State_Failure

I have a Dell XPS L502X. 18 months old, running windows 7 home premium.

It has started hanging when shutting down. It just sits there saying 'shuttiung down' for several minutes and then crashes with a Blue Screen of Death with the messaage Driver_Power_State_Failure but no other useful information.

I have tried many things including a factory reset but still this problem is appearing. Before I get desperate and reformat the hard drive completely and reinstall from the recovery discs, does anyone have any ideas?

Dave Smith