As usual, cut and paste your f1graphics.bat in another folder and run GP4, if it runs, you will need to re-define all your options.
Else, keep your f1graphics.bat and ecrase your gp4.exe (you can make a backup before) with a save of the decrypted exe and try again.
This matter comes at 90% with one of these two files which has been "corrupted" noone knows why.