If I run a script that was made or downloaded before the problem started, it runs without the error. As I said, the problem started right after I started using Mando3DWrite, so it's not just my own scripts (I'm not saying Mando's script caused it, that's just when it started happening).
I'm starting to think it's just that Vista doesn't like OFP very much. I had a problem a few months ago where Vista would not allow me to save changes to scripts, description files etc, in Flashpoint mission folders. The permissions would be automatically altered, and it would not allow me to change them, despite being an administrator. I had to cut/paste scripts to desktop, alter them there, then paste them back into the folder. That problem seemed to fix itself though.
ALSO, I've been having another problem with the ground textures being corrupted or something. I'll be in-game, and suddenly the whole ground texture will turn black with white markings, the most recent one being black with the word 'Policie' from a nearby police car suddenly tiled all over the landscape. I used to to think it was just on user-made maps, but it happens on stock islands as well.
I think maybe I'll have to take Flashpoint out to the woodshed and shoot it.