Hi Mike Elnar,
Currently, not all themes we ship in our suite are compatible with the new Visual Style Builder we released as of Q1 2010 and the Aqua theme is one of these themes. We will make sure that we migrate all our themes to the new theming mechanism in our framework so that our customers will be able to open and edit them in the Visual Style Builder.
However, you can still extract the currently available built-in themes by selecting the Extract Built-In Themes
option from the File menu option in the VSB.
You can also refer to this help article that is a good introduction how you can work with the VSB:
Getting Started with the new VSB
I also suggest reading the other help articles regarding the VSB since understanding the concepts behind it are important if you wish to be productive with it.
I hope this helps.
the Telerik team
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