I've been experiencing this as well. I did some looking, but I didn't see any other threads with this issue.
I was routing a bunch of ponds together with channels for some watery Fun after a few rains and I had all traffic outdoors just stop... I had probably 20-something cut lumber sitting around waiting to be hauled and my three or so miners just standing next to channeled tiles with No Job. One of the miners was "trapped" between two ponds after he channeled himself in, so I (thinking like it was 40d) ordered a floor be built so he could get out. Someone eventually came and built it, and I think that's when everyone first 'froze'. I re-ordered the tile the stranded miner was on to be channeled, which he did, and went and climbed out on one of the ramps. At that point things seemed to move again for a bit, everyone came out to pick up lumber, etc. But then it happened again. No stranding issues this time, just a bunch of miners next to their channels with No Job. That's about all the relevant details I can think of for this particular instance. Oh, I did make a backup save at this point in case it could be useful in the troubleshooting.
On a potentially related note, on a separate project much earlier in the life of the fort I was digging down the 40 some odd levels to level 100, found a cavern with some Fun I wasn't ready for yet, and ordered a floor built over the stairs a couple levels up. Now, my excavation was a 1x1 shaft of up/down stairs. The dorf built the floor on the same level that he was, and I would THINK this would mean you wouldn't be able to go down on that stair, but you could go up. Not so, apparently. He got stuck. I ordered a side shaft be dug to him, but I kept having problems with unreachable cancellations. It seemed like they were trying to path through the blocked stairs to some of the tiles nearer the trapped dorf, instead of through the side shaft that they could actually access. I was eventually able to change around the designations and time it so that they came in from the "right" side and got him out, but definitely strikes as a bug needing fixing.