Hmmm, the main cause of the lag was fixed. What type of machine are you on? Also, is it 3fps in the upgrade screen, as well? Or just when playing?
Oh wow, even when the game lagged it didn't lag that bad! Let me look into it...
If you want to restart the game, it won't load your game again, but there is a cheat you can unlock by pressing:
u d l r a b s
on the menu screen (in the upgrades, the up arrow will give you 10k coins each time you press it)