You sure it's a working server you're joining?  3 known working servers are: RSF 16p Server, RougeTribe.com and BlackIntel.org

If you are crashing on those servers, try the following:

Try deleting FirstStrike.exe in your install folder.  Start your launcher again, try to play the game.

Failing that, delete *all* the builds this time, in your 2142 install folder/mods.   Start the launcher, go to file -> Preferences, set version to "1000" hit apply, then okay.  Click launch, wait for the updating to finish, attempt to join one of the working servers from up the top of this post.

Failing *that*, go to your 2142 install folder /mods and delete the "First Strike" folder.  Reinstall First Strike.