Have you tried another SD card yet? Is this your first ROM? Have you put that SD card in another phone, or if not available, an SD card reader? That could help give you some indication as to the state of the card, although I wouldn't rely on that alone to test.
I have toyed around with multiple ROMs on my HD2 and never had an SD card problem, although in the past I have had a card die when doing some modification on my G1. Also, if you are still using the 16gb card that's packaged with the TMOUS HD2, it may be a decent idea to consider replacing it anyway. It's only a class 2 card, and while that may suffice for many operations, it really suffers when you're trying to use an app like QQPlayer to apply software decoding to video.