Looks like a severe case of divitis ... ;-)
... but looks certainly cool.

Have you tried to use a less complex design, just strip it down to your basic layout and working your way up?

Since you code in XHTML, I would
- use the STRICT variant
- code for FF, debug for IE

In my experience, a valid XHTML STRICT page which works in FF works almost equally well in IE6 and needs minor adjustments for IE5 (depending on complexity).

hth,
Alex