If you have the web dev tools for FireFox, outline table cells and you will see the problem as the logo is theoritically restricted to the confines of the table cell.
If you are concerned about IE on the MAC, check user statitics as I believe that this is down to less than a percent of the users on the whole. And it is IE 5 Ick!!

Another might have a work around for IE but as you do not have much that can not be completely copied over I really suggest that you consider upgrading. A second install with another DB would make this easy and is the recommended method for any live site.

If you upgrade now, to Version1.3.0.2 "highly recommended" you can view this thread for how to center the logo
See this thread:

Centering the Logo