For some reason, since this morning, Firefox will no longer open PDFs in tabs on my Mac. I'll click on the link (or right-click 'open in new tab'), the page will open, display the pdf interface at the top, but won't load. Occasionally the grey loading bar will move across slightly and stop, although usually nothing will happen at all. If I click on the Document Properties section at the end, it gives me no PDF or file information whatsoever. The most confusing thing is that if I click on the PDF link and select 'open in new private window,' it will open the PDF as per usual - although I don't want lots of new windows open and would rather be able to stick to using tabs. I work through a lot of PDF's at once and having them all together is fairly important.

I've double checked updating Adobe, I've double checked updating Firefox. I've checked on the preferences menu to ensure that PDFs are set to 'Preview in Firefox.' All of these are fine. I've also cleared my cache and restarted everything a few times (just incase). I've also used Chrome and IE just to make sure it's not a file problem, and as expected, these load the PDFs fine. Does anyone have any idea why this has suddenly started happening?