Actually, REDUCE your cache!
The cache is an old idea from the beginning of the web when 'fast' was anything over 9kbps. So, to load a page you have been to before, your computer first looks in your 'cache' to see if the page is there, and if so, grabs it instead of the one on the Internet, thus looking like your system is faster.
But, with fast Internet speeds, try actually reducing your cache (with all I do on the web, mine is set at 10mb, not the tons it defaults to) and change the settings to get a new page *every* time.
I am guessing you hit our site when the new menu bar was, well, new. It was quickly updated to be FireFox friendly and should be fine for you.
Hope this helps.