I've had some of these same issues.
I've had a Vibrant since it was released last July. On previous versions of the OS, I've had various other issues, but recently I have been have new issues, probably associated with going to 2.2. In the last 2 weeks they have sent me 2 new phones that both have the same issues.
My main issue is the Media:
I am having the issue where videos and music just won't play anymore. This is both on internal and external memory. To be sure it wasn't the files I was putting on, I try to record a video and that no longer works either. Incidentally, I can still take pictures.
To resolve this, I have to restart the phone. I suppose that wouldn't be so bad if it didn't happen withing a day. I don't think it is reasonable to have to shut down the phone every day. Am I the only one who thinks that?
I'm about to call back in to support to see what they say. I'm pretty sure it is going to 2.2 as this time I'm not using an external memory card, an installed very few apps, none of which have anything to do with media.
I had this same issue with my first phone. This is very frustrating. I have barley had phones 2 and 3, so maybe that problem will creep up, I'm not sure. It was also something I noticed more recently and was probably due to 2.2.