That's strange. It seems with that base tag and src in the img tag that it should load the same file you're able to load in the browser. Did you try a different browser? Maybe use something like Firefox with Firebug to see what the browser's trying to load when you load the page.
Otherwise I'm out of ideas.
ETA: Just read your post above. There may be some Firefox setting telling it not to load the images by default. Do you get images on other sites?
Every other site including my own. I have no idea what's happening anymore.
It must be just my browser playing up. What page do you get when you load the site on FF?
and also I keep getting random database errors when I refresh forum.php