So, I was testing the SMC and EFI updates by not turning off my machine for around 5 days. It works perfectly, no more "not waking from sleep" issue. During the 5 days, I never left the machine to sleep on its own (with the lid open). I just close the lid when ever I want it to sleep. Today, after installing the 10.5.6 and do the restart. Everything seems to be perfectly fine, except that the machine won't sleep, on its own. I tried restarting, and changing the sleep settings in the energy saver preference, but still now luck. The display still sleep, exactly at whatever time I set it to, but the machine just won't. Also, I already tried leaving the machine idle for 5 hours, but no luck. I am suspecting that this is probably cause by the 10.5.6 any body has the same issue?