What machine are you seeing this on? Its easily possible. I've had temps over 200F on my MBP while using Garageband or rendering video in iMovie. That is on the MBP C2D, non-unibody.
That temp is within the threshold of "normal," albeit at the upper end of the spectrum. Your machine will shut itself down to protect itself when/if it exceeds it's threshold, (which I don't know what that temp is).
What were you doing while you saw that temp?