You're using the Deviance trainer, I suppose? The only time I got the thing to work reliably was using the very first version of the that trainer, with the unpatched version of the game. It's not worth all the bugs. I'm aware they updated the trainer to work with a later patch, but as you and others have noticed, it hardly seems to work.
The other options (save editor, item editor) that Raze mentioned earlier in this thread are your best bet.
