Crash at the login screen

I'm only asking this here because I'm getting tired of being asked to check the same components by tech support with Blizzard.

So, my video card took a nosedive, so I got a new one and reinstalled Sep 29th (a maintenance day).

The system now crashes at the login screen. The screen comes up for a couple seconds and then straight to a black screen and reboot.

No other stability problems at all with any game. PSU is well above what is required. Latest drivers currently. I've tried older drivers, different combinations. Reinstalled the game. Temps are quite cool. Loads are low. Memtest says my memory is good. The inside of the case is clean, etc... This problem is happening on a screen with very little demand on the computer.

The only thing that helps is deleting the Config.wtf file. I do that and it starts up as normal and I can play indefinitely without any problems at all. In fact, I can keep portions of the Config.wtf file and still restart, although it seems to change sometimes just how much of the file I can have in place before it crashes.

I was just curious if anyone else has seen this or has any insight. At this point I'm putting my 4 boxing on hold and just playing a single priest while I wait for Windows 7 to be released, when I'll give it another try.

Sorry, have never seen anything like that.