As with the last version I hear the "Trainer Activated" and when I press the keypad buttons I hear "ON" or "OFF". This works with the latest Steam version of the game at of 12/7/09. Curious if you have anti virus running, if so look in its logs and check to see if anything in the memory is being blocked. McAfee has the ability to do that I an made an exception/rule allowing open access for all the games I play.
My only problem with Steam remains that I can't turn off auto updates. When I turn it off it appears to stick but when I check back later its back on again. Not sure if that's the trainer or just Steam, I'll say its wonky Steam interface stuff.