So pretty much i tried all the obvious. i went into device manager and made sure under keyboard and mouse the Allow device to wake up computer is checked on. In my bios, i cant find anything that deals with power management for usb/wake/keyboard and mouse etc. when the computer goes to sleep i can only wake it back up with the power button. sometimes the fans turn on but no post and i need to hold the power button for 5 secs. other times it successfully resumes the computer.

what can be the problem?