NHL99 seems to be a very sensitive game. I had problems when my bus was overclocked to 83.3 MHz which disappeared when I switched back to 75 MHz. I had problems when my Savage3D was running at 136 MHz that disappeared when I switched back to 130 MHz.
If anything in your system is overclocked, I'd try turning it down and testing with that.
The game runs very nicely with a Savage3D, actually.