The leaks are happening in FireFox.

I think you were one of the first people to figure out the huge IE leaks with closures and COM elements, though there are other types of leaks affect both IE and Firefox. Here is a link at Mozilla:

http://www.mozilla.org/scriptable/avoiding-leaks.html

That one is the best and most complete description of how JS code leaks. A little over my head, but ought to be great for you!

They fixed some small things starting with Mozilla 1.8. Here is the log of the guy that writes the Leak Monitor:

http://dbaron.org/mozilla/leak-monitor/

And if you wanted to be real hard core:

http://www.mozilla.org/performance/leak-brownbag.html

Unfortunately, I see the 1MB per page on our own site with the menus too, and about 30k leak without the menus (I'm working on that one).
:(