Does the money value even stick if you close the game and trainer, reboot your PC and just launch the game?
It's the health one, it was mentioned earlier in this thread.
What worked for me was turning off Max Money, saving and reloading my game; then I was able to research new items again. Worked for me, hopefully works for you too.
The Set Money is actually Max Money, which is what you see in the instructions. A new trainer will be sent to fix this GUI error. Due to the way the game works and the trainer works, the trainer has to work the way it does. Toggle the option on, then load a game and you have the max money. I won't be changing the trainer to make the money editable, for many internal game engine reasons. I spent a LOT of time with this annoying game and there are reasons why this has to be.