Check your stand by voltage (+5SB)http://www.antec.com/Believe_it/product.php?id=NTg=
Also check the USB devices connected to your PC. You may be overloading some of the port. At sleep/power sving mode only the +5SB is used to power whatever is on the USB port(i.e. keyboard, mice).
Its common that the USB ports are overloaded.
Recovery or wake up is dependent on the stand-by supply.