Hmmm.. this is really puzzling but when I switched to rev K (on 4.01 M33-2) I had to re-install it again. I know you have already done that but sometimes it works like a charm. Just make sure that you delete EVERYTHING NitePR from your MS first.
What game are you trying to use it for? If it's FTB2 and you DL'd the 1.6 patch I would suggest that you delete the 1.6 patch and just use the server for 1.5.
This is the DL for rev. K that I used. Prolly won't matter but I know this one works.

http://www.megaupload.com/?d=W5AF6GI6

Also IDK about DC7 but the easiest way to downgrade to 4.01 M33-2 is with pandora.