Odd effects on page load

Hi

I’ve just creadted my first WP site for a client; it’s just basic static content, rendered as pages.

The problem is that in IE, when navigating through the site, the menu turns to a grey bar shoing the id ‘navigation’ before loading. Could this be a theme (Woothemes Canvas) issue, or is it a WordPress thing?

It works fine in Firefox btw:

http://mercedesaguirrecastro.com

Thanks very much in advance.

Jez