When I have "acquired" videos from some place like that I always make sure that I'm choosing a format that will play on my PlayBook before downloading them, MP4 as an example. I use software to convert any that are not PlayBook friendly though if that isn't an option. There are some free ones available. Here is a link to a thread that may help.
I've not really had any problems with briefly borrowed movies/tv shows. Avoid mkv but most avi's seem to play without issue. Just copy directly to the pb's Video folder using computer and usb or wifi sharing.