[JohnF]

Alrighty - I had a few spare moments this morning.

Shut down, unplugged, and pulled the first stick of RAM. Plugged in, booted up (since the power was off, it booted cleanly), shut down, turned back on, and encountered the same problem.
Repeated this by putting stick one back in and pulling stick two. Still the same problem.

So I suppose my question at this point is: why would BIOS ver. F6 cure this problem, where F4 and F5 do not? What's the difference? (The description for F6 on the Gigabyte website is "Improve ET6 compatibility." I don't even know what ET6 is.)
Is there any way to know why F6 is not stable on my system / any way to make F6 run stable on my system?

(I also notice that there is a F7a listed in the Latest BIOS sticky thread. I'm hesistant to flash to something I assume is an alpha product, and really hesistant to keep flashing the BIOS. I've probably done it too many times already.)