We have an older installation of DNN (6) that until yesterday had a working library of PDF files available to our customers for download.  Then we got a report that there was a problem downloading some of the links.

Upon investigation the first eight links were throwing 404 errors, but the rest appeared to work.  And even the ones that didn't work by clicking the link were available if you removed the &forcedownload from the link (the PDF would render and then you could click the file icon from the adobe view).  We tried resetting the app pool; that didn't fix it.  And to make matters worse, by the end of the day nothing from that page would bring up the PDF (including the aforementioned work around).

Other pages have links in the same portal directory structure that work (at the moment at least) but nothing on this page does any longer.

We have tried the following so far: 

• resetting the app pool.
• resetting the DNN applicaton.
• using the file manager's "sychronize files" function.
• adding some of the files back in manually.
• confirming that all of the file permissions are correct and have not changed.
• checking the DNN database to ensure it is responsive and updating OK.

And nothing above has helped or pointed us to a solution.