USB Mouse Jerky Tracking - Software Issue? I have two Logitech MX510 mice, and two macs - an iMac and MBP. Recently, the former has started responding to mouse input jerkily and without any precision - to the point that it is almost unusable. Switching out the mouse, rebooting, etc make no difference. 

Similarly, both mice function fine over a long period of time attached to the MBP. The only change I have made to the iMac (2012 gen, OSX10.8) is to install Crashplan - but I did this on the other computer too and that made no difference.

Is there anything I can do to flush out the settings for the mouse, and so return it to usability? The problem does not occur with the wireless magic mouse, or the wireless trackpad.

Thanks!§
Could you have different mouse drivers on the iMac than the MBP?

Try to install the drivers from Logitech, or remove them completely, see if that makes a difference. You can also install a 3rd party driver like USB Overdrive.