I'm 100% sure it's image references, I've had this problem before on other forums that I managed and when you investigate you see it's usually images for buttons, smilies, that sort of thing.
I'm hoping this week at work isn't as grueling and I don't get any more news bombshells dropped on me so I can actually get some work done on... well anything. Been a rough week so it's been very unproductive for me.
Anyway, will keep everybody posted as I get through the CSS and forum software code.