FLV prog download playback problems

I have been using flv files for nearly 2 years on my website, but recently have seen a significant number of problems relating to playback. Most of my flv files are 5 mins long, but it seems that many of these are stopping early and the cue point on the preload bar just skips to the end. I have received many complaints like this but the point at which they stop and skip seems to vary so it doesnt seem like a direct problem with the flv file. When checking myself i find that everythings plays without problems.

They are simple swf players, embedded in an htm.

I am compressing using Sorenson Squeeze 4.0 . I am on a ds73 dedicated server. Linux

Traffic on my server has been increasing dramatically so Im wondering whether this could have anything to do with it. Any thoughts?

heres a url to a screen grab of my settings. Any feedback on this would be appreciated
http://www.fevah.org/adrian/

Many Thanks
Adrian