I don't know if it stopped working in Firefox 16 or 17. Maybe the problem is related to the fact that I've two entries in Options->Applications for PDF documents.

Perhaps you have opened or saved a PDF file which had an incorrect MIME type.

Have you installed some other extension/add-on to view pdfs? The entry that we insert is the one that says "PDF (Portable Document Format" and it should be set to the option "Preview in Nighly/Aurora/Firefox" (translated of course). Or maybe this could just be another case of bug 777388?

Reproduction steps: 1. Open a locally saved PDF file in Firefox with Windows Explorer. Verify that pdf.js works. 2. Save´this attachment file 3. Attempt to open a locally saved PDF file again. Result: Opening a locally saved PDF no longer works. A duplicate entry was created for PDF in the content type options. There is no way to enable pdf.js again for locally saved files in the Firefox UI, other than the reset Firefox button in about:support.

Getting rid of the "ask always" option would probably solve this. If the user wants Firefox to always ask what to do with this content type, simply delete the entry from the content handler options.

This is no bug in pdfjs but rather a very old bug with bad entries in mimetypes.rdf. This caused earlier only bad mime-types submitted in http post (for example uploading a pdf or word document).

Should this bug be closed?