Can't import movies on a specific project

Hi everyone.

I'm having some troubles when i try to import a movie on a specific project. At best, i get a black video, at worst, it can't even read the file and give me the following errors :

File couldn't be read. Error reading encoded movie (buggy encoder ?) [Assets/Movies/ship_cockpit.mov]

Problem is, if i create a new project and try to import my movie, it will work. Tried to do the same on other existing projects and it worked too. This is the ONLY project where i can't import movies T_T

I tried to do this with a lot of formats, and i even tried to create a package with my movie from a project where it was properly imported, but import this package will result in the same issue.

Any idea why this specific project is having troubles ? What should i check ? What parameters could be responsible ?

I'm on Unity Pro 4.5.3f3, btw.

Thanks in advance ;)