I know this won't help much right now, but 2142 crashing should not be caused by First Strike, since the mod installs to it's own mod folder and does not affect any core 2142 files. You also didn't mention which version of 2142 you have.
Read ALL of the rest of this post before taking further action.
Since it sounds like something has gone wrong though, it may be worth reinstalling 2142. Did you have Northern Strike involved? Patch 1.51 as you may know includes the NS maps so there is no longer any need to install Northern Strike seperately or to validate it.
When you reinstall, please ensure you are using the correct version of the 1.51 patch (there were two beta versions I believe before the final release).
Install 2142 (without Northern Strike)
Install patch 1.51
Ruun BF2142 and ensure it runs, also try to join a server to force a punk buster update.
If you have issues, go to the evenbalance website and manually update punkbuster.
Install First Strike, run it to update the launcher and the mod.
When it has finished updating and asks you if you want to launch the game click no.
Now click on the launchers file tab, then go to preferences, in the arguments field enter either +widescreen 1 or your own custom resolution like this +szx 1920 +szy 1080 substituting the numbers for your own res to enable widescreen or a higher native resolution.
Now launch the game again and check your server tab. If they are red (as they currently are) you can try this:
Go to your 2142 installation folder (program files(x86)/Electronic arts/BF2142) and locate two files, the firststrike.exe and the bf2142.exe (sometimes also called 2142pace or 2142launcher depending on version). Copy the 2142.exe to your desktop and then rename it to firststrike.exe (make sure the name matches the current FirstStrike file in the 2142 install folder). Now move it back to your 2142 folder to overwrite the existing FS file and check servers again.
good luck!
Bite my shiny metal Tie Fighter!

