my partner had a problem with wandering mouse pointer. It kept bugging her but every time she called me through to see it, it stopped moving. Later, when she came through to put her mouse battery on charge the penny dropped. After changing the battery in her CORDLESS mouse earlier in the day it had to be re-registered with its usb dongle and in doing so had ened up on the same channel as my mouse, thus when I moved mine it moved both our pointers.