Streaming .flv video stops and gets back to the start

We have recently created a flash site in which a page simply opens a video using the video player and streams it - nothing else there.

The .flv movie is only 20MB (inside a folder in the main root of our server) - it starts loading fine and it streams, but after it reaches half of it (the movie is 3 minutes long), it simply stops and gets back to the beginning (you can press play to start it all again).

If I play the movie and stop it right away to let it load the complete buffer, the buffer starts loading slow but fine and suddendly it loads in one go to the end of the clip (it would have to take longer, like when it began). This is a sign it won't work -> if I click in the end area of it, no frames show (the end of the movie) meaning nothing has been buffered in that area.

The first days when we uploaded the site it all worked fine but now the movie stops - the buffer loads at one point in one go (bad sign...).

What could it be the problem? This is a professional flash template we are using. I've tried using a .mp4 (h264) movie and the same happens...

Cheers