Picked my bike up today from the LBS after receiving its tune-up. I took it for a quick spin in the parking lot and it seemed to be running great. Took it home, and after dinner decided to take another quick spin around the block. I'm riding around and I start to hear a faint whining noise. Finally, I figured out it was coming from the back tire and I see that the back tire is rubbing against one of the chain stays. I don't know anything about fixing bikes, so the only thing I could do was loosen up the wheel a bit, then I was able to get it straight again. However, once I rode it again the tire immediately when back to that position.

I guess I will have to take it back to the bike shop because I know it wasn't doing this before I brought it in. Anybody know what the problem is and whether I could take care of it myself?

P.S. I am attempting to upload a picture but, conveniently, Photobucket is deciding not to work for me right now.