Refreshed by not enough sleep, I went back to the problem this morning and discovered that I was unable to look up any of my dimension members in the map that I'd created for the purpose. What the heck?
After investigating a whole lot of possible points of failure, I found that the case-insensitive map that I'd hacked together was looking up the case-insensitive keys and storing the case-sensitive keys due to an error in typing.
Well, that won't work!
*thud* *thud* *thud*