What error message(s) do you get?

If you right click the link you posted above to the PDF and click "Save link as..", saves the file to somewhere on your PC and then tries to open it from Explorer, does it work?

It says DONE or STOPPED and provides a blank screen... it does not ask to download. Then if you wait long enough, you get another error that says: there was an error opening this file.... both screen shots are in the attached file.

If yuo hit refresh like maybe 5 times it will load.

link to PDF http://www.namescape.com/Portals/0/CaseStudy-University_Library_Staff.pdf

this PDF opens in all other browsers tried. Opera, Safari, Chrome, IE.... just not Mozilla Firefox.

I removed all my Adobe suite yesterday. Cleaned all the Acrobat files. Reinstalled the files. Made a new PDF, posted the new PDF and the only browser than cannot open it is Mozilla.

Try "Reset Download Actions": http://kb.mozillazine.org/File_types_and_download_actions