I see what's wrong but I don't know why this happens - I've seen it happen two or three times in the last year or so. I suspect that this is caused by a different edition of Freelancer to the one most people use.
You should have a file called content.dll in C:\Program Files\Microsoft Games\Freelancer\DLLS\BIN\ but it's not there, instead the file is in C:\Program Files\Microsoft Games\Freelancer\EXE\ and it shouldn't be.
To fix the problem, copy the content.dll file from the exe directory and into the DLLS\BIN directory and all will be well.
(and if someone is feeling really motivated start a wiki page with this kind of information in it)
Proud member of "the most paranoid group of people in the community"