Just a quick look, but shouldn’t your right column be floated right instead of left?
Otherwise I find it’s usually quicker to start with a known good layout and incrementally build it, vs. debugging that can go on for ever…
Here’s a css layout resource I use quite a bit…tho it’s timing out at the moment (*really* hoping it’s not gone):
http://www.inknoise.com/experimental/layoutomatic.php
FWIW, Firefox is much more standards-compliant than IE - meaning if you get a layout that works in both Firefox and IE you should be covered pretty well.
