Hm, I tried making a new pilotfile, going to the mission simulator in the tech room and pressing ctrl+shift+s but nothing happened.
Also, I don't know if that error you're seeing is because I'm only using some of the mediavps, namely the 3613_Update.vp, MV_Assets.vp, MV_Effects.vp andMV_RadarIcons.vp. I tried running the game both with all mediavps as well as mediavps disabled entirely, but the problem persists.
But thanks for the help. I'll appreciate it if you ask one of the SCP guys to take a look at this.

EDIT:
Ah, ctrl+shift+s does work indeed - I must've pressed ctrl+alt+s or something at first.
Anyhow, creating a new pilot and loading the mission from the mission simulator did away with the problem. Curiously, so did restarting the campaign with the pilotfile I've been using all along - so it wouldn't appear to be a corruption in my pilotfile would it?
EDIT2:
Also, just earlier today I tried running with the most recent nightly build. Could that be what caused it, even if I switched back to 3.6.12?
EDIT3:
Before I restarted the campaign with my pilotfile, I made a backup. With that backup I tried suiciding five times to advance to the next mission. The next mission is screwed up as well, it seems.
I'm guessing my only option is to restart the campaign. Is there any way to skip the missions (another key-combination perhaps?) until I get to 'A Game of TAG'? I'd rather not have to go through the task of suiciding my way through all the missions, and I'd rather not play them in the mission simulator either.
Or is there at least some simple way to suicide?