This happened to me last December and I can't remember how it was resolved, not on this forum as I've been back to check.
I have a vague memory (most of the time) that I eventually had to raise a new profile, but why should FF13 suddenly lose the pictures in this magazine and on e-Bay etc,. yet switching to Internet Explorer 9 solves it, but I prefer FF as a browser.
All security programs have been run and ASC.
Adblock is disabled and tried turning off all add ons but to no avail.