So, this must be a bug, as the behavior doesn't make sense, and I can't figure out how to "trick" LR into seeing the folders again.
If I launch LR, the first time I import, I can see all of the root folders in a particular NAS share, and I can see an arrow next to the folders that opens the sub-folders.
If I import, then initiate another new import, those sub-folders become inaccessible via that import browser, however, I can browse to "other location" and point directly to the sub-folders, so I can still import the content.
Would be nice to not have to do that step. Is there a fix?