I was getting this too.. Press "i" for Inventory, no prob - then pause, and hit F1 to activate trainer, Esc back to game and press "i" again - crash.
I was going to try switching back to the original EXE since I'm using the Reloaded EXE, but thought I'd try the other trainer first - even though it says it's for AUS+UK/English and I was using the U.S./English one, and bought my game here in Canada - and loaded it up and no problem! I can bring up the Inventory with the trainer activated and have been using it for the past half hour with no further crash.
So I'm not sure what's up and what's different - I thought/think that my Exe is the US one not the AUS+UK one, but not sure... So thgouth I'd mention it in case it might help anyone else.
Cheers
The Aussie+UK version also fixed this issue for me. Works perfect now, I am a alien mutation killing machine.