Which Setpoint are you using? there's a disk that the mouse comes with that has a specific version of the Set Point client meant for the Logitech G500 and G9 mice. If you downloaded Set Point off the website then it might not work.
Hmm, I had the exact opposite experience than nin-ha. I had many problems when installing setpoint from disc, especially when it came to updates and the like. Every time I started setpoint I had to re-associate my mouse to the software. My recommendation is to uninstall setpoint completely, then visit logitech support >> http://www.logitech.com/en-us/support Follow the instructions in option 4 or download the auto-detect function in option 1. Then install the latest version for your mouse. Good luck.