Help! Strange build/buy mode lag/glitch!!

Firstly, my computer specs are:
Windows 7 Ultimate 64-bit
CPU: AMD Athlon II X2 245
RAM: 4.00GB Dual-Channel DDR2 @ 401MHz
Motherboard: ASUSTeK
Graphics: 2047MB NVIDIA GeForce GTX 680

I have the base game plus all expansions and packs bar 'KP Sweet Stuff', 'Fast Lane Stuff' and 'Into the Future'

So, the game was running perfectly fine, other than there is a strange glitch/lag with the build/buy mode. When I move the cursor around to try and place an object, the object can't 'catch up' with the little box that places it (if that makes any sense) so I'll try and put a plant onto a desk and the box where the plant should be when I'm moving it into to it's location is moving all over the screen with the actual plant glitching around for a few seconds before it catches up. It's unbearably annoying and is making the game near-on impossible to play. When this error occurs it sometimes makes the game stutter a bit and zoom in and out of it's own accord.

I use Advanced System Care Game Booster and I've tried changing the graphicsrules document in the game file. I don't know what to do, any help would be greatly appreciated!