Yeah, water main break. The A, B, C, D, E, F, J, M, and Q trains were all screwed.
It was kinda nuts--every train I got on seemed to have a completely ad-hoc route. Not just "the F is running on the C line", but "THIS F is running on the G. The one behind this one is running on the A, but is making these two additional stops." Hence all my changes. I'd get a few stops closer, then the route would change and I'd have to figure something else out.
When the first screw up happened, I debated just going home and working from there. Am regretting not doing that now.