Upgrade attempts foiled by hanging, freezing

So I've got an ASUS M3A motherboard (AM2+, AMD 770 chipset) with an AMD Athlon X2 4200+ (2.1GHz, AM2, Brisbane core). I recently decided to upgrade to an AMD Phenom II X4 945 (3.0GHz, AM3, Deneb core). (further specs on request.)

Here's what happened:
* Removed OLDCPU and put in NEWCPU.
* Attempt boot. No POST beep, blank screen.
* Put OLDCPU back in, restart, boot Windows.
* Check ASUS forums, discover that I need to update BIOS.
* Flash BIOS to v.1206. No problems running Windows or anything with new BIOS.
* Put in NEWCPU.
* Attempt boot. This time, I at least get a POST beep and can reach BIOS menu. BIOS recognizes model of NEWCPU. Save settings, exit.
* Attempt to load OS. (Dual-boot, Windows 7 x64 Pro and openSuSE 11.2, with GRUB as the bootloader.) Trying to scroll through options on GRUB with arrow keys causes bootloader to freeze. Trying to boot from default option, Win7 partition, causes reboot without ever seeing Starting Windows screen.
* Put OLDCPU back in, restart, boot Windows, create forum posts.

Based on what information I've provided:
1) Is there anything I've neglected to do?
2) Is there some compatibility issue I've ignored? (I'm aware that this combination is not officially supported by ASUS (yet), but I've read that people have combined similar processors with my model of board and had virtually no trouble.)
3) Did I just receive a bad unit?

Need to RMA this to Newegg if necessary before September 6th, so any help would be appreciated.