Two things I've experienced that appear to produce your results... Check where the receiver anttenae (the one attached to the computer through a USB port) is located. I've found that if this is moved too close to the computer it can cause the mouse to be erratic. Secondly, try changing the batteries in the mouse. Even if one doesn't receive an alert displayed on the monitor of low batteries, the battery condition can cause the problem. I said two, but perhaps there is a later driver for your mouse that you can download. Check the website for the mouse manufacturer...Best of luck!