Ive got a g5 and its a bit of a pain sometimes if you play a bit of extended gaming...like bf2.
I tend to grip the mouse with me thumb on the left side, and the ring finger (right hand) on the right side of the mouse to lift / use it. The moulding on the right side of the mouse hurts a little after a while. Try hold it yourself, see if it does the same, or try a razer mouse...