It's not Firefox 5.
Opera 11.5 does it too, and I'm virtually certain that it is (at least in part) a caching issue. Opera has always had very aggressive caching for performance reasons, and the latest versions are fasterr than ever ... but sometimes they can trip over their own feet. Firefox 4 and 5 (which last is really 4.1 but the idiots can't get their version number system working properly) also are very aggressive on speed optimisations. They are the first Firefox versions ever to challenge Opera for speed, and it seems pretty clear that they are having some of the same sort of issues.
One thing you can do to force a clean load is change the address. For example, edit
http://www.ausphotography.net.au/for...loading-issues to read
http://www.ausphotography.net.au/for...oading-issues& or
http://www.ausphotography.net.au/for...ading-issues&& You will still get the exact same page, but the extra "&" (which makes no difference to the server) forces your browser to fetch the page anew.
If these issues persist after the new server goes live, I'll be a little suprised.