I managed to get my x1950 pro all the way upto 117 while playing bioshock and it ran without any issues...but i kept exiting the game just to be safe (this was a few days back...before i got rid of the dust that had clogged up). now the max it reaches is 70 while playing any game including bioshock and Idles at around 41-43.
Jesus to me that's bloody hot. Have you set the thermal shutdown option within your ATI control panel? Basically your GPU will throttle itself back to avoid damage.
The hottest my 7800GS+ Golden Sample reached is 65c although I do have 2x 12cm fans (front/back) and 1x 8cm fan on the side. Do you have plenty cooling on your case?