I wanted to play Ares again after a wave of nostalgia. So I promptly downloaded it and booted it up, only to have it lag uncontrolably in-game for no reason.

Anyone know how to fix this? Using an iBook G4 with the latest version of OSX Tiger, running Ares under classic enviroment.

Nope. It hasn't been fixed as far as I know, nor is it likely to be.
Ares worked in Classic under 10.2.8, it never worked usefully under 10.3 or later.
There was an updated version which improved things slightly but not to any useful degree.
I boot up in OS9 when I want to play it