read the thread on the sprint clean up tweak, I think a lot of users are having issues when using this. I think the problem you are having is related to something called the Microsoft Screen of Death. I would suggest fully reading the clean up thread, there is a lot of good info in there. Also there is a stock sprint 6.5 thread floating around with a lot of fixes and tweaks (i'll grab and post the link here shortly).
*link*
http://forum.ppcgeeks.com/showthread...t=sprint+stock