This problem seems to develop and be solved a bit differently depending on how Pro Tools LE v.5.1.1 has been installed to your machine. First scenerio:You install Pro Tools LE v5.1.1 from a full install CDROM. Simply remove the PACE file from the MP3 codecs folder and restart. Second scenerio: The machine has Pro Tools LE 5.1 on it and then the Pro Tools LE 5.1.1 LE updater download has been run on it. If you then download the MP3 option 1.1.1.0 for Win and you're getting prompted for a floppy auth., the fix is to Uninstall Pro Tools LE 5.1.1 and then reinstall Win Pro Tools LE 5.1 from the installer CD. Then download the MP3 option for 5.1. After you get the MP3 option authorized you then need to download and run the Pro Tools LE 5.1.1 updater for Windows.