I experienced the following problem. I think Leopard users should pay attention.
Symptom:
In gaming, suddenly the game speed turned to be extremely faster. The 'p' (pause) key worked but '-' (decreasing speed) key was of no use. The blinking of button was also faster. When I terminated the game, everything turned to be normal state.
Cause:
I found ntpd program adjusted -0.5 sec. at the same time when I got the trouble. I confirmed the same symptom occurred if I set the system time backward a few seconds while the game was going on.
Avoidance:
The problem may occur if you turn on “Set date & time automatically†in System Preferences. So turning it off avoids the problem. I'm not sure it occurs in all Leopard Mac. As of OS X 10.5.2, I guess Leopard's ntpd has a bug. Its behavior looks odd.