Having Trouble With iMovie

Hey guys,

I am having a problem I need some help with. I have just started doing some free lance work for a really great company, and they asked me to build them a simple intro for their online videos. I made a quick 5 second intro in Sony Vegas 11, exported it as a 1920x1080 MP4 file, and uploaded it into their dropbox for them to use on their videos. I have also made a short film in the same format filmed with a 7D (.mov files) and they get the same message.

The problem is, they are having trouble importing the intro clip into their timeline (they use iMovie). The error message says, "The operation couldn't be completed. OSStatus Error - 12909." Does anyone have any idea what is going on, or what I should to do to smooth this out? This is a great opportunity, and I want to make sure I do a great job so they'll continue to assign me projects.

Can anyone help me out a little bit? It would be greatly appreciated! Let me know if I need to provide any further information.

Thanks in advance!