I have problem with my n810. I want to click on left appliaction menu and lunch some application. BUT, menu is empty, so there is no app, moreover there is no category (for example "Utilities, Settings, ..). I don't know why it is, but I can't lunch any application from menu (e.g lunch "Backup" for backup all settings and then reinstall OS).

Please, can someone help me? Thanks for quick suggestion

First thing's first, please remember to search. This question has been answered before and it saves both you and everyone else a bit of time if you look before you post.

The solution is contained both in that thread, and in this bug report.

In summary, your filesystem is too full, remove some stuff you don't need.