If you put a RadTabStrip on the same page as a RadSpreadSheet the controls of the TabStrip expand where there is a lot of white space. I can't provide a screenshot but it's definitely the RadSpreadsheet causing the issue.
I'm not sure if there is a way to isolate the two. I've tried Asp.NET Masterpages, Divs, Spans, etc.
Perhaps overriding the CSS.