|You kind of answered your own question. If the doubleclick setting has no effect it must be either a defective mouse or a software issue. Software issue can cover alot of ground.|
I suggest you try a different mouse on your computer and try your mouse on a different computer. If your mouse works on a different computer try remove all entries for mice in Device manager and rebooting. If you have dedicated software for the mouse try un-installing, rebooting, and re-installing.