Is this a webpage that contains a link to a flv file? Please post a link to the page and tell us which link(s) are the problem flv files or else post a link to the .flv file itself.

Alternately, click on one of the sample FLV File links on this page and tell us exactly what happens:

http://www.mediacollege.com/adobe/flash/video/tutorial/example-flv.html

It might also help if you post the exact error message, including the path to the flv file.

Note: Depending on how you have Firefox set up, clicking on a FLV File link will either save the FLV file to your computer or Firefox may open it automatically in an external application right after downloading (Firefox may ask you first). Firefox itself can't play FLV files so you need a "helper" application (or a plugin for flv files, if ther is one. You can see if Firefox is already set up to download or open FLV files by going to Firefox Preferences and looking in the Applications list. Find the FLV file type in the list and, if the action is "Open with", it should show the application that can play FLV files (e.g., VLC Media Player or Perian). See Managing filetypes for more information.

Thanks for the assistance. I did not include the file path because the flv files are in a Learning Management System course so you have to be enrolled to view them. The files have been in use for about a year and since they worked in Safari I knew there was not anything wrong with the files. I later checked them on my laptop and the files played in an older version of Firefox. I found an old installer for Firefox 7 and replaced 9.0.1 with the older version. The files now play without any problems.

I'm glad that the problem no longer exists after downgrading to Firefox 7 but that isn't a good solution. Firefox 9.0.1 includes a number of improvements, including security and stability updates as you can see from the release notes here: http://www.mozilla.org/en-US/firefox/9.0.1/releasenotes/

Just so you know, I tested the FLV example links on the page I posted earlier using Firefox 9.0.1 on my iMac running Os X 10.6.8 and I had no problem. For example, when I click on the link to http://www.mediacollege.com/video-gallery/testclips/20051210-w50s.flv Firefox asks me what I want to do with the file 20051210-w50s.flv and the option to open with VLC (default) is selected. When I click OK, the .FLV file opens in my VLC Media Player application and the video plays.