crap I just read the fish lice thing.....it sure sounds like it. 

Hrm. Did you see any more of them swimming around the tank? That's how the fish lice work, that they're "jumping" around from fish to fish, and in some cases they cause smaller wounds on the fish's skin when sticking for long to one of them.
These are rather difficult to kill and need to be treated with Dimilin or Program. But before I tell you anymore about either of them (Dimilin is a pesticide and Program is a medication for dogs to get rid of lice) it might be good to ask at the pet shop for some suitable medication to kill these lice with.

Just so you know, I checked out treatment methods in a book I have that's written by a veterinarian who specializes in goldfish, so he might just choose some treatments that are a bit advanced for a "normal" fish keeper d:

Salty,
I use something called Paracid.  I treat all new fish for 3 weeks as a precaution.  You can add it directly to the tank and it won't harm the eco-system of the tank.  It is really safe to use for fish and it kills all kinds of parasites.
Any aquatic pet store would probably have this or something similar I would think.

Yeah, I first got the medication when some of my pond fish had fish lice.  With one treatment the lice crawled off the fish and died.  It was recommended to me by a person who is a professional at ponds and goldfish and koi.
I was amazed how well it worked!

yeah, that's the stuff I just picked up. I just put in the first of the 3 recommended doses per the box, so hope it works!