Is your firefox cache disabled?
Mine is for some reason, and I haven't even changed a setting and I've seen this on other computers too.
To check, type about:config into the address bar and then type cache into the filter.
If your browser.cache.disk.enable is bold, your disk caching is disabled. Click to enable and the value should read true.
Before:
After:
If your browser.cache.memory.enable is bold, your memory caching is disabled. Click to enable and the value should read true.
Before:
After:
Please post here if you're cache is disabled, so I see I'm not the only one
and please post any web-developer extension you have installed (FireBug/WebDevToolbar).
Mine is for some reason, and I haven't even changed a setting and I've seen this on other computers too.

To check, type about:config into the address bar and then type cache into the filter.
If your browser.cache.disk.enable is bold, your disk caching is disabled. Click to enable and the value should read true.
Before:

After:

If your browser.cache.memory.enable is bold, your memory caching is disabled. Click to enable and the value should read true.
Before:

After:

Please post here if you're cache is disabled, so I see I'm not the only one

and please post any web-developer extension you have installed (FireBug/WebDevToolbar).