We would like to have a more detailed issue description.
If you hear this sound, do you see any messages within the Operating System stating the USB device has been disconnected or even reconnected? Is the system freezing? Does it happen only with the mouse or any other USB devices? Do you see any yellow bangs within device manager? Which Operating system do you have? Was the same behavior presented when testing the USB mouse on ever USB port? Etc.
Furthermore, as a general recommendation, please proceed to perform a BIOS Recovery update to discard a corrupted BIOS. Instructions can be found here: http://www.intel.com/support/motherboards/desktop/sb/CS-023360.htm
Also, for testing purposes, please run the system in Safe Mode in order to see if the problem replicates to determine if this is at a software or hardware level.
Thank you for the reply. There are no message, just a disconnect-reconnect sound. It reconnects as soon as it disconnects. I have the device manager open to see what happens, and it looks like something disappears and reappears. I can't tell what it is because it reconnects too fast. It happens with my mouse and my keyboard. I can't type or move my mouse during this ~1 second event. There are no error messages. I've included a screenshot from a program called USBDeview, which records USB events. You can see where a few devices become "unplugged' and "plugged back in" at the same time.
I'm running Windows 7 64bit. I will try the safemode and BIOS recovery but please let me know if you can think of anything else. Thanks!