Wireless mouse & keyboard does not connect at startup

I bought a new computer and bought a Microsoft 3000 wireless keyboard and optical 2.0 wireless mouse. When I first start the computer neither the mouse or keyboard connects
even after resetting the connect buttons on the receiver, mouse & keyboard. If I connect the oem wired mouse to the usb and use it then the wireless works. It continues to work after restart but not after being off for awhile. Any Ideas?