Well, besides your code, which I feel relies on javascript for absolutely no reason, (other than your beloved pre-loader

) -
Your navigation is quite tired and dull, as well as being a jumbled mess of tables and js calls without
any option for those with javascript disabled, such as myself.
It would far more managable/accessible/less code/better looking
if you used an unordered list <ul>with links <a> nested inside the list elements <li>. You can see a
very basic example on
my links site , and if you go to the CSS links section there are far better examples from places like a list apart, SimpleBits and others.
Also, when you redo your nav. with <ul> and CSS, put equal padding on left and right of <a> text so as to centre the text within it's display block. Perhaps a 1px solid border around each button slightly darker than its background as well as a narrow margin to seperate each would make them more aestheticly pleasing.
And don't forget to assign a different colour to a:hover{color:#......}
so the link text changes colour on hover. This is an important visual clue that should not be removed.
!important
If you really want to keep the sliced images and lay the page out in the traditional way, use Adobe ImageReady 7 for the slicing/exporting.
It has options which allow you to get it to make all slices <div>'s and all styling CSS. This is a fantastic option for those trying to make the transition from chopped up tables to flowing em's or wherever.
Just make sure you set it to ALL LOWERCASE tags and attributes and to make the slices background images of their parent div, allowing you to freely add other elements into the div later.
SOme of this may not have made much sense, but I wrote the second half assuming you had gone and done everything I recommended in the first half
Have fun redesigning,
Andrew
**edit: Image Ready 7. Don't remember if 3 could as well. (ver.3 shipped with Photoshop 6)