I am having a similar problem except when I view my page locally (IE 6,XP Pro, IIS). The calendar is displaying horizontally across the entire screen. Also in Firefox 1.0(locally - IIS and Tomcat 5), there is a big empty space next to the 'next year' and 'next month' buttons, which are stacked instead of side by side. I can fix the IE problem in the style sheet(*-system.css) but it doesn't fix the Firefox issue and they may be related (as if I know..).

I hardly ever post to forums but it's a great calendar and we really want to use it in our web app.