Hi Oleg,
Here are a few things I would like you to try:-
1) Create a new workspace using File > Switch Workspace, to something like C:\tempworkspace
2) Create a new Java project, put an error in the Java file… do you see the annotation in the package explorer?
If NOT, then it may be an installation problem. If you do, then you should switch back to his old workspace, then restart using -clean, if that doesn’t help it may be a configuration issue.