Look at this thread and go down to “If you cannot Boot the computer”.
YES, I know it is a VIRUS removal thread but I have PMed one of the experts for you on helping on these boot/BSOD issues.
He will run some utils, etc. to help but will want to see FRST log.
Download and run the Farbar (FRST) and post the log(s) to this thread.
http://forum.avast.com/index.php?topic=53253.0