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Problem: The latest Q2 2010 SP2 release greatly improves RadStyleSheetManager and it now combines style sheets registered after AJAX updates. By implementing this functionality we inadvertently broke the scenario when your page does not have a <head> element. Now all style sheets registered with RSSM fail to load if this element is missing.
Solution: The problem will be fixed in the next internal build (version 2010.2.1001+).
Workaround: Add a <head runat="server"> tag to your page.
Solution: The problem will be fixed in the next internal build (version 2010.2.1001+).
Workaround: Add a <head runat="server"> tag to your page.