In an Eclipse SVN project I have a problem; when I tried to open a declaration of one class, I got this error:
Problems opening an editor Reason : projectna
It happens, when libraries are not available on class path of the project where F3 does not work. Select any other project and try to use f3 for navigation. It will work.
The solution is to add JAR files in your libraries or add libraries in your project. Try to use MAVEN project so that the problem can never occur.