Can't select controls on my form

The problem can occur when a new version of DevComponents.DotNetBar is installed and the old version is still referenced from a separate library folder.

The app and all DotNetBar referenced dlls should be re-referenced to the latest version.

Just right-click the form and uncheck Lock Controls.

Well, I kind-of solved the problem, although I don't know what the actual cause was. In my program I'm referencing devcomponents.dotnetbar dll. I removed the reference and then re-added it, rebuilt the program and now everything's working in the designer as it should.