Yep, same boat as the previous poster the (Mega Trainer 188.8.131.52 (10.07.2010) Updated:10/12/10) no longer works (STEAM version) after yesterdays update. Gives crash dumps once an option tries to activate.
Anti-virus is disabled so it has to be due to the update.
Update: Could not get the new one released today (Mega Trainer 184.108.40.206 (10.12.2010)) to work either. Crashes just by using any command in single player campaign.
Error is: Crash! Access Violation (0x....)
Some more info: 1) These trainers used to work with the steam version before yesterdays update without problems.
2) System is clean of spyware/malware (According to Avira) and all firewalls, anti-viruses, and antimalware scanners are disabled/turned off. All firewall settings and ports are cleared with the game anyways.
3) UAC is turned off so all applications have administrator privileges.
4) System is Vista x64.
5) Trainer was started prior to launch of game and activated only at the main menu.
6) Steam services have verified integrity of game cache (0 errors) and defragmented the game cache.
7) Game runs 100% for hours without errors without trainer.
8) Crashes just by having the trainer activated, but no options are pressed.