Thanks everyone...

For completeness, my blood work thus far (all "normal"):

CBC/Chem, ANA direct, sed rate, B12 795 pg/ml, CK 127, free T4 1.2, TSH 1.27, Acetylcholine receptor Ab (all), Lyme IgG/IgM, IgM quant, CK again 151, Aldolase, Phos & Mg again, CK again, Proteins incl. electrophoresis, T4 and TSH again, intact PTH, Autoimmune serology (RF, Smith, RNP, SS-A, SS-B), and more proteins/immunofixation (IgG, IgA, IgM, monoclonals).

I don't believe in the word "Idiopathic", although as a veterinarian I know that that is where a diagnosis sometimes ends, but there must be a cause somewhere. I'm still stumped by the muscular fatigue that I know I can induce with overexertion, predictably followed by several days of fatigue. Cortisol? A (micro)vascular problem? I've also checked my glucose during those episodes looking for The Simple Answer.