[F4U-1_Corsair]

that would indicate that the mission is lacking the mission file, and has only the proporties file which means the game thinks it is there. The first thing in the mission file is what map to load, but because there is no mission file, It comes up with the error you mentioned.

Try finding another copy of the campaign, and extract all the missions and replace the ones you have. Your campaign progress is stored elsewhere so it won't be damaged.

See if that works, if not, send me a PM with a copy of your campaign and I'll see if I can fix it.

EDIT: I just realised you might be refering to a Dynamic campaign, if it is, I can't help you.