Yeah that is pretty hot, how long does it stay at those temperatures? 100C could possibly cause some damage, but it is actually pretty unlikely. 100C is a lot, but most cards I heard have a pretty high threshold, sometimes topping almost 125C.
Also, are these temperatures this high while normal use of the computer? Or is this during gaming or other heavy GPU related tasks? Because if it's idle at those temps, the chances are your peaking the cards threshold, and probably going over 100C. Need more info about what your doing though to be more certain what the situation with your video card.
I still would take JDFAns suggestion, and make sure your fans are plugged in and working, because running at those temps, many people still consider dangerous, and probably is.
To answer the question blatantly though, I don't think your card is going bad, its just having poor circulation of air flow. I could be wrong though... we need more information