Sorry, i forgot. The version of Sharpdeveloper i´m using is 2.2.1 Build 2648. I´m using c#.
Recently i experienced that by renaming controls in design view the developer deletes control declarations of other controls, too.
[EDIT] I used an old project, changed the project options, but i did not rename the project file. That seemed to be the problem. After renaming the project file and the namespaces to the actual project name seemed to have fixed the problem.