I've tried looking everywhere for a couple of days before opening a new thread here, but it seems there aren't any similar threads around.
In case I'm wrong please forgive me.

Changed the usb polling rate from 125 to 500 mhz,twice,using usbmrs 1.1.
Had no problems whatsoever the first time (roughly 9 months ago),and restored the old usbport.sys back to 125 'cause I didn't like it at first.

I changed it back to 500 again last week and,since then, only when I play Quake Live, the mouse randomly stops working every 3-4 minutes or so: it will turn off (= the sensor "light" disappears), and after 3-4 seconds it comes back to life.

When this happens I hear that windows sound you get when you plug/unplug something via usb.

I tried changing ports and unplugging/plugging the mouse again, but I get an error message about the installation of the device.
Tried restoring the usbport.sys file +doing again the usbmrs thing, problem persists.

OS: windows xp
mouse: mx518

Is there any chance to get it working without having to format?