Hi John,
I recently posted the same problem here under "strange mouse behaviour"
First advice I got: disable tool tip information for the menues, that worked for me.
Second advice: Stop all applications running in the background which are not necessary before you start playing, best achieved with Enditall (but be careful with that tool).
This improved the entire GP4 performance significantly.
You may read the above mentioned thread for more details.
Good luck,
Markus