I have seen valve stems freeze up from using wet air out of a compressor. The expanding air drops in temperature and freezes in the stem. This can happen in temps warmer than freezing but it will quickly melt. At sub-freezing temps it could persist.

If you have a problem with the valve stem sticking or leaking at the valve (not at the rim) you could always just change the valve. Buy them and a valve stem tool at any auto parts place. Beats having the tire unmounted and remounted.