Got my rear tire back from the bike shop yesterday. They replaced the broken spoke, stress-relieved and re-tensioned the wheel gratis.
Put the wheel back on the bike last night, and went for a quick ride this morning before the rains return today. Legs felt like lead. I was struggling to maintain my normal speed, and inclines felt like mountains.
Some of you are already giggling, knowing what happened.
When I took the wheel off, I had to loosen the cable on the rear brake, because I could not get it to compress enough to get the cable guide out of the slot. I put the wheel back on, and tightened the cable back up. Spun the wheel, and it was smooth and dead true.
If I applied the rear brake, and then released it, the brake wasn't centering, and the right pad was dragging on the rim. So I rode my quick ride this morning with partial rear brake application the whole way. Doh!
It's adjusted properly now (Thanks, Google). Seems I just needed some resistance training this morning