Tech Issue - Not City

I'll join the long list of those hoping to benefit from your collective wisdom.
When I try to use Youtube the search results show blank boxes instead of the initial frames of the videos. However the boxes still work as hyperlinks as clicking them starts the videos.
This has only started happening recently. Soon after it started I noticed a banner telling me my browser (very old version of Firefox) was out of date and wouldn't be supported much longer so I updated to v3.6 but the problem persists. It works OK in IE6.
Any ideas?
I found a comment on a forum about something similar happening but that was with a page that had loads of pictures each acting as a hyperlink. The victim didn't name the site but said it wasn't an "images" or photo-hosting site, and mentioned that another site set up in a similar manner worked OK. The issue wasn't resolved in the forum so I can't copy the solution.
All suggestions gratefully accepted.