Sick Cory?

Hey guys, one more question..(sigh).

I have an albino cory catfish that I've had for about 3 months now, but he seems very off lately. I noticed him becoming less active-he used to scamper around the tank all the time, now about 3/4 of the time he just lays there. The other day I noticed he was kind of tipping over when he was swimming, but I haven't seen him do it again. Levels are fine, and I haven't done anything different or introduced any new fish. I don't see anything apparantly wrong with him, other than the fact that he is lethargic. I have a heater in there and it is working fine.

One of my female swordtails did this before I got the cory, a while back, but looked much worse (although no tipping over), and eventually died. I hope this one dosen't have the same thing?

Any ideas are appreciated. :)