Had a similar problem: Freecorder just stopped recording, showing only a flat line.

My error was not starting Freecorder before loading the webpage. You don't have to hit 'Record', just push 'Pause' to bring up the little wave box. Then navigate to, or reload your page.

It was explained to me that Freecorder detects the audio files as the page is loading, and cannot detect the buried audio file after the flash app has loaded.

Hope this helps.

M.