Gimp and Wacom

I've had a look around at others queries but I can't seem to find anything that has helped.

I have a Wacom Bamboo Fun tablet and for some reason, it lags and does strange things when I use it in gimp, but for Sai and other programs it runs just fine. I've looked in preferences and all the settings are right, but I can't seem to figure out why it doesn't work in Gimp.

Any help on this would be very very much appreciated!