Have you configured the transmitter with the keyboard and mouse? Usually it requires a set sequence.
You could also try Uninstalling the keyboard and mouse in Device Manager and then rebooting. Windows will then Find New Hardware and reinstall the drivers.
One other point. Optical mouse don't like dark or patterned surfaces very much (for obvious reasons) and I have to tape a sheet of A4 white paper to a mouse mat for it to work as it should.