This is also happening to me. Everytime flashgot sends a link to jDownloader (JD2), it will try, at least, 3 times to communicate with the program, resulting in this "File Exists" messages.

I already tried to remove both jDownloader and flashgot (clearing also the about:options in firefox) and also disable the kaspersky firewall, but with no success.

PS: Btw after all the tried FG pops up this message: "JDownloader not responding on **External links are only visible to Support Staff****External links are only visible to Support Staff**!. Please check your firewall settings."