Well, this is an odd turn of events. I'll give the whole story here and add a summary at the bottom.
I reclaimed an old site, which was a small glacier located in the middle of a forest and, shortly after un-forbidding everything with the bookkeeper, my miner ran into the underground and got shot with a blowdart.
This wasn't a problem until later, when I designated a hospital and the miner, in true dwarvy fashion, ran to the Hospital crying and plopped down in the corner of it before I could even add a bed. The local doctor comes to help him out.
Here's the catch. My water supply isn't working properly. I think I have it figured out, but basically, it's an aquifer that's in a dirt layer right below the glacier and the hospital can only be reached passing through the glacier. I figure the water is getting frozen midway, because the doctor is constantly carrying a bucket back and forth. And no, this isn't the old medical bug, because the miner is getting thirsty and generous, hardworking dwarves are carrying buckets to him, to no avail.
Thankfully, the hospital was in a rock layer, and I decided to build a reservoir near it, using the aquifer, when the most annoying glitch happened: the dwarves refuse to mine.
I've got two picks, one is attached to the wounded miner, and the other isn't forbidden. However, no matter what dwarf I assign, they simply refuse to mine. They've got nothing else to do.
Summary: Dwarf injured. Got thirsty. Need to mine to get water. Miners refuse. HELP!