Sorry to hear you have been experiencing problems.
I just tested the HD cumshot clip for Alessandra Leite & Rico Puentes and it worked okay for me.
Please try updating your version of the DivX codecs to see if this helps - you can download the latest ones from
http://www.divx.com/en/downloads
I also usually use VLC Media Player which you can download for free from
http://www.videolan.org/vlc/ - it is a great video player which tends to handle anything you throw at it!
Please try these and let us know if you still have problems.