For the fact that it was on overnight should be no issue, ive left my system online for 2months at one point while hosting a server.
If you had turned it off, I dont see anyway it would have switched its self on for no reason at all unless you put it on sleep mode.
With the Blue Screen on Death, have you changed any hardware recently? or moved around any cables inside the PC?
and also, is there any way you can get to Safe Mode as it boots up by pressing F8.