I'm not playing games on these computers. It happens even with no apps running at all other then something as simple as - for example - a File Explorer window. The mouse will act fine over the main window, but when I click on "New" and try to move the mouse down the list of the pop-up menu it begins to lag (eg I can move my mouse down to the last choice and it will take the cursor more than 2 seconds to catch up. Once the cursor makes it out of the pop up window it then acts normal).
I have, however, now noticed that every now and then, maybe for about 5 minutes or so at a time, this actually stops happening and everything seems normal. I am currently in the process of trying to determine a difference in the state of Windows when that happens (using System Explorer and kdif ) but haven't had any success so far.