What version of IE?
Try adding the following CSS rule: html, body { height: 100%; width: 100%; margin: 0; padding: 0; }
The other thing you could do (though it might seem heavy-handed) is have a BorderContainer as your top-level element and have the TabContainer as the region="center" part.
<div dojoType="dijit.layout.BorderContainer" style="width:100%;height:100%">
<div dojoType="dijit.layout.ContentPane region="top" style="height:60px">
...
</div>
<div dojoType="dijit.layout.TabContainer region="center">
...
</div>
</div>
I confess I can't try this in IE as am on Mac but have been doing loads of dijit layout lately and something like this should work.
Michael B
2009-08-13 23:53:20