Check your asus bios file at the post screen; see if another newer file is available; don't flash if you already have the latest file. You'll need a usb flash drive to update the bios. If you brick your board with a bad flash, request an rma from asus and tell them simply the board won't post. No other info is necessary. http://www.asus.com/Motherboards/AMD_AM3Plus/M5A88M/#download.
You may also rma your power supply.