I have exactly the same issue (posted on a previous page), cgminer freezes on middlecoin only, both on BAMT and Win7. My suspicion is that due to frequent switches/disconnects cgminer is more prone to issues and is ready to go over the edge at any time. I've installed the latest ATI drivers on my BAMT box last night and it didn't freeze when a cgminer on my Win7 box did (11:35 PM PST), but showed a huge drop of kh/s at that point in time.