I've had a similar cache problem with FireFox when I upload a new version of a music file to a web page with a link to the MP3. I've tried , & Clear Cache, usually without success -- I still get the old MP3 playing. I'll try a couple of the tricks above.

I suspect my problem is caused by one of the many add-on plugins, likely the download "helper", they're so tempting but sometimes more trouble than they're worth.