So here's the deal:
I was working with Kojak, preparing to go in game and get my stuff switched to start work as a trial mod, and about the time we go to climb in game, I realize that 2.1 had opened SA Single Player, not SA-MP.
So, I tried again. Same result. Trying re-installing 2.1. Same result.
Then, I went to install 2.2, and it worked fine, but when I went back to 2.1 so I could access Argonath, it continued to open single player, not SA-MP.
Kojak suggested that I wipe out all existence of SA-MP on my computer, and re-install from scratch. I did so, and continued to get the same error.
Overall, my trial as a mod is being delayed because of this, not to mention that I can't get on Argonath whatsoever.
If anyone has any ideas, let me know.