HI, I have a PowerMac G5 Quad (4 X 2.5 GHz PowerPC G5, 4.5 GB DDR2 SDRAM). I recently upgraded from OSX 10.4.11 to Leopard (10.5.1). Now when the computer goes to sleep, it refuses to wake up. The fan also comes on at high speed. Any help anyone can suggest would be appreciated. Thanks in advance. Pete