Well, temptation rears its head and I was unable to resist the siren call of these beta bioses after all.
Thanks to the guest who chimed in in this thread about what 5fg was doing with the Crossfire PCIe slots--I solved the problem. That's all it was--I removed the second card--have a new one coming Thursday anyway replacing my venerable 590/480 X-fire setup--and, viola--I can now get into the bios because F5g is at least intelligent enough to properly configure a single GPU... Thanks again, who ever you are, for the tip. I would have found this out later--maybe--but it's so much better knowing what it is! As Clouseau would say, "Problem solv-ed!"