It finally clicked, after a rewrite of the controls in the game and deciding the code was working fine. It hit me, it's the physics!
iGrow Game uses PhysX and it should now download automatically when launching the game the first time.
Incase it doesn't you can download it here:
http://www.nvidia.com/object/physx-9.15.0428-driver.html
Happy Growing!
- iDev