Thank you for you information.
We had just published a new version 2.0.87 that fixes several issues in VS2008 design-time environment (plus other enhancements). Please download it from http://www.zettacube.com/Downloads.aspx.
If you encounter further problems in VS2008, please kindly let us know.
Update (2009/4/1): Certain MS Hotfixes are required to resolve some design-time issues. Please refer to the "Setup on the development platform" section in the installation guide for details. Moreover, please update ZeeControls to the latest version.