Could you be over your 1 GB data limit for the month? That would explain the slow internet and problems with YouTube. The market will time out and not load if your connection is too slow, but mine still usually works even after throttling. When people talk about the "speed" of the phone, they are usually more talking about smoothness of scrolling through screens, speed of opening menus, and stuff like that, not really internet speeds which depend on the carrier and your signal strength.