Hi,

One reason could be that some websites may store the cache as TMP files in the Windows current user temporary folder instead of the browsers's cache folder. Another reason could be that the media is being partially streamed, deleting the already played parts while streaming the next part.

The same files which do not store in Firefox Cache will store in IE... I prefer Firefox when ever possible...

You can try to check if the video is being fully stored by using a stand-alone cache viewer. eg. VideoCacheView Please note that this is an unknown application. Many security software may flag the site or the software as suspicious. There could be many similar applications.