Computer "looses" USB devices when busy

I have again and again the very nasty effect on my computer that it "looses" the mouse when I start a specific, very CPU intensive task.

By "loosing" I mean, that I hear the ding-dong sound as if I had unplugged my SUB mouse, it then (of course) remains unresponsive for like 30 seconds and then I hear the dong-ding again (as if deluged) and then things are more or less back to normal. This happens reproducibly when starting up a very CPU-intensive application, which, alas, does its main job as a Windows "service". Apparently these have higher priority and then not only cause the system to react slowly but even so slow, that they can't handle USB devices properly any more.

Since I didn't find any way to lower the service's priority: can one alternatively somehow boost the USB-handler's priority, so that it's higher than that of the service? If so: how? And what driver or executable would that be?

Michael