I've seen a couple posting saying they were having the same problem with the wireless mouse that comes with the Lenovo Enhanced Performance Wireless Keyboard and Mouse
Problem: After a period of time the mouse goes into a sleep mode while the keyboard appears to be functioning. Sliding the mouse back and forth does nothing to awaken it. Most people report having to mash the little yellow sync button on the mouse and usb dongle.
Solution: Pick up the mouse just far enough to break the surface that it is sitting on and 'drop' it back down. Mouse turns back on.
I've tried the above steps several time on three seperate setups that we have and it has worked each time.
