Thanks, that did help. However, no matter what I do I cannot get the navigation to display correctly in all the different browsers, as pretty much none of them render lists the same way (and yes, I’ve tried CSS resets).
So, I’m just about done wasting my time with coded templates. If a template works perfectly in all browsers, and is fully W3C valid, then I don’t understand why I have to code it exactly how ThemeForest prefers.
So, I guess this means I’m permanently out for coded templates, and will be sticking to PSD only (unless any coders out there have any interest in this: http://themeforest.net/forums/thread/looking-for-a-partner-/16374 
).