Sudden mouse lag

[cadmaster]

Sorry if this is repeating other posts, but the ones I have looked at aren't quite the same.
My problem is that mouse lag has appeared suddenly. I use a Kensington Expert Mouse trackball, USB version and when I move the ball there is a short delay before the cursor follows, though the delay varies. I can't think of anything that would have suddenly introduced this, other than a virus/malware but I have BitDefender installed and there have been no notifications.
There doesn't appear to be a setting in the Windows Mouse panel for this - is there a Registry entry I can check?
I use this machine for CAD work, so this is not only extremely annoying, but potentially costly in lost time in having to redo things because of overshoots etc.

 

[carwiz]

Just to make sure, down load and install the FREE version of Malwarebytes Antimalware. Don't click on the "Trial". Let it update then run a full scan. It's quite common to pick up malware from just visiting an internet page. Many third-party ads placed on a page are not controlled by the owner of the site. It's imperative that your AV be updated daily. Not to mention an updated OS.

Also check your startup applications for strange programs. You can see these by clicking on the Orb (Start) then type msconfig in the search box. Press enter then click the Start Up tab. Below is a sample. DO NOT disable programs unless you know what they do. Some may be required by your OS and hardware to function.