What could cause "2A" code on 890FXA-GD70 mainboard?

Question

My MSI 890FXA-GD70 now stalls at the point where it displays the code "2A."  Can someone describe the possible cause(s) of the mainboard stalling at "2A"?
I even contacted MSI and received a refurbished mainboard, which I installed this weekend but it presents the same error.
I observe that all other lights and all fans appear to be working just fine, but I never see any video at any point (no MSI splash screen, no BIOS, etc.) during the brief boot process before it reaches the "2A" display.
I have tried two different PCI-Express video cards and neither one changed the mainboard's behavior of stalling at "2A."
My computer worked flawlessly for nearly three years before experiencing this problem.
Here are my PC's components:
   * Microsoft Windows 7 Professional 64-bit 1-Pack for System Builders - OEM
   * SAMSUNG Spinpoint F3 HD103SJ 1TB 7200 RPM 32MB Cache SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
   * Crucial 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory Model CT2KIT51264BA1339
   * Crucial 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1333 (PC3 10600) Desktop Memory Model CT2KIT51264BA1339
   * ASUS Black 24X DVD+R 8X DVD+RW 12X DVD+R DL 24X DVD-R 6X DVD-RW 12X DVD-RAM 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM 2MB Cache SATA 24X DVD Burner - Bulk - OEM
   * CORSAIR Enthusiast Series CMPSU-650TX 650W ATX12V / EPS12V SLI Ready CrossFire Ready 80 PLUS Certified Active PFC Compatible with Core i7 Power Supply
   * MSI 890FXA-GD70 AM3 AMD 890FX SATA 6Gb/s USB 3.0 ATX AMD Motherboard
   * Cooler Master Hyper N520 Mirror Finished Copper Base Aluminum Fins 5 Heatpipes CPU Cooler
   * AMD Phenom II X6 1090T Black Edition Thuban 3.2GHz 6 x 512KB L2 Cache 6MB L3 Cache Socket AM3 125W Six-Core Desktop Processor HDT90ZFBGRBOX
   * COOLER MASTER Centurion 5 CAC-T05-UW Black Aluminum Bezel , SECC Chassis ATX Mid Tower Computer Case
   * XFX HD-567X-ZNF3 Radeon HD 5670 1GB 128-bit DDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card
I also tried swapping out the XFX video card listed above with the following, purchased new:
   * SAPPHIRE 100358L Radeon HD 7770 GHz Edition 1GB 128-bit GDDR5 PCI Express 3.0 x16 CrossFireX Support Video Card
In addition, I tried installing both video cards in different PCI-E slots on the mainboard, in case one of the PCI-E slots has gone bad.  (I even tried booting without any video card, and did get a different code, but I can't remember what it was.)
I tried all of the troubleshooting steps described in prior threads related to the "2A" code, such as:
https://forum-en.msi.com/index.php?topic=145187.0
https://forum-en.msi.com/index.php?topic=151534.0
That includes swapping out RAM sticks, including one at a time.
And I also dutifully followed all of the suggestions offered by an MSI technician by telephone.
I even plugged in different keyboards (PS/2 and USB), different mice, etc.  (Grasping for anything that might present a different mainboard code at this point!)  But nothing makes a difference.
Any other ideas?
Should I just request of MSI a new RMA# to get yet another refurbished mainboard?  (The MSI tech I spoke to previously about this "2A" code seemed convinced it was a defective mainboard when he authorized the first RMA.)
Or should I just keep buying new video cards until I install one that works?  (I only have one desktop PC with PCI-E slots, my other active desktop PC uses AGP.  So I can't verify that the video card works in a different PC; I can only trust that buying a new, highly-rated video card didn't result in the bad luck of getting one that was DOA ... but I suppose theoretically that's possible, however unlikely.)
Thanks!

Answer 1

I'm still unable to get past this code "2A" stall.  Can anyone help?
Among the troubleshooting steps I've tried since my February 24 post, none of which made any difference/improvement in the stalling at "2A":
Unplugged all SATA drives and power connections to those drives (2 hard drives and 1 CD/DVD drive) and tried to reboot.  Result = stuck on "2A"
Unplugged all external peripherals (e.g., mouse, keyboard, ethernet, etc.) and tried to reboot.  Result - stuck on "2A"
Unplugged all external peripherals and all SATA drives and tried to reboot.  Result - stuck on "2A"
Unplugged all front panel connections - except the connection to enable the power button needed to reboot the system - and tried to reboot.  Result - stuck on "2A"
Disconnected all power supply connections, except the CD/DVD drive (to put a small load on the power supply), and tested out the power supply with a volt meter (multimeter).  Result = 100% of the molex, 24-pin, and other power supply wires are delivering the expected volts.
Are there any MSI representatives available who can provide more detailed information about what the "2A" code indicates?
I found the following information about code "2A," but I'm not sure whether it's applicable for my specific MSI mainboard, on a PDF provided by American Megatrends (BIOS company) titled "AMIBIOS8 Check Point and Beep Code List" from 1988:
Quote
Initialize different buses and perform the following functions: Reset, Detect, and Disable (function 0); Static Device Initialization (function 1); Boot Output Device Initialization (function 2). Function 0 disables all device nodes, PCI devices, and PnP ISA cards. It also assigns PCI bus numbers. Function 1 initializes all static devices that include manual configured onboard peripherals, memory and I/O decode windows in PCI-PCI bridges, and noncompliant PCI devices. Static resources are also reserved. Function 2 searches for and initializes any PnP, PCI, or AGP video devices.
Thanks!