"I have 120 to ground on A phase, nothing between B and ground and 120 between A & B. "
You may be measuring through the connected load on B through to the neutral? (poss phase loss on B)
Are you using a DMM, a solonoid, or neon tester? Solonoid or neon, and your probhably getting 90 - 160V, and it may look like 120V between A + B. (poss phase loss on B, or lost neutral)
Any recent gardening?
Corrosion?
Bad CB?
ETC.......
Anyway, it's a possible high low voltage hazard, hope you didn't leave it connected in this condition?
