Video problems in Quicktime from limewire

[Sc00p]

I've downloaded some large movie files (about 200+mb), and it only plays the first two seconds of it in quicktime, as though the movie were 100k, even though the completed file is full-size. I would say a good 80% of the files I download do this.

...I only get this problem when downloading from limewire, any ideas? Could it be Quicktime 6's fault?