It could be problem with the mouse driver. You could go to the device manager, right click the mouse and look at properties to see what's wrong. If the driver's corrupted you can manually remove the driver and then re-install the driver. Depending on your OS and your luck windows will find the driver by itself.
As for the warranty, it really depends on your nation but i believe that if you have a proof payment with date from your bank/credit card company they are obliged to accept it, though they'll be reluctant.