The maps are installed in the levels folder. I can see them in the Map list as you described. I cant actually start a local server (no doubt a Vista X64 issue) but thats another matter.
Even though the maps are physically there, whenever I try to connect to a NS game online I get the "You must purchase Northern Strike from EA Link" screen.
Just tried clearing the cache, still the same. Ive also tried 2 different browsers.
Ive just got the EA Downloader (as there is no EA Link anymore). It correctly lists 2142 Deluxe as one of my games as well as some BF2 Boosters which I bought years back.