I am not aware of a BSOD crash in 4.2 while closing the program. When saving assets, a new temporary file is created and written to until complete then the original file is overwritten at the end. This usually avoids such corruption problems, but it is hard to tell. At any rate, I am glad you had a backup so you are back up and running again 
Edit: BSOD crashes are often due to hardware failure. One thing to check is to make sure your drivers are up to date.