Agreed. I'd check for a BIOS update for the motherboard. If it's up to date, try entering the BIOS and loading the default or fail-safe settings and restarting. Re-enter the BIOS afterward and check all settings, making to sure to adjust other system settings accordingly (boot order, hard disk IDE/RAID/AHCI mode, memory timings, etc.).
ASUS's website lists version 1004 as the latest BIOS. It includes an updated AGESA version, which is what identifies and sets parameters for CPUs. The only other version they list that contains an AGESA/CPU update is version 804, so if you're running something earlier than 804, it's likely unable to properly ID and setup that CPU.http://www.asus.com/Motherboards/AMD_AM3/M4N68TM/#download