When in seamless mode, you should have the menu available in the task bar, like in the screenshot. It is one pixel high when not in use, but mouse over to reveal - as per screenshot.
You can uninstall Virtualbox, and you won't lose the actual VM.Would it be a good idea to reinstall? Would i lose my vms?
[qoute]I installed 4.1.18 from the software center because I failed installing the 4.2 from the oracle website.[/QUOTE]
I have never used that method, but guest additions are also in the Software Centre. You could try installing from there.