Are you running the 4GB patch?
Might be a RAM Problem.
Edit:
From the MFM read me:
Quote:
If you use GWX or another supermod,
install this mod AFTER the supermod - it contains important updates for ships that I released earlier, such as the Empire Freighter and the CAM-Ship.
This mod should be compatible with virtually all other mods - it simply adds new ships to the game world and does not change game mechanics or environmental files.
If you get error messages, try installing this mod on over a new career and/or clean install.