We are already aware of the bug that you encounter with the Visual Style Builder when using the Black skin as a base skin. We are currently working on the issue and most probably it will be fixed after the up coming Q3 release of our controls. We apologize for the inconvenience.
Considering the your other question related to the height of the RadMenu control I would recommend the following help article that explains in details how this can be achieved using the right css class selectors for the menu - How to change height of RadMenu
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed