Comment 6 for bug 821586

Thanks Frederik. I've installed a fresh partition with Oneiric and German as the default keyboard layout. This did the trick, it's easily reproducible.

At first glance Onboard appears to react correctly. The system actually changes the keyboard map from "de" to "us". The keys displayed in Onboard and the keys sent on clicking seem consistent.
Now, why the keyboard map changes, I have no idea yet. Will dig deeper.

Another bandaid: running
    sudo dpkg-reconfigure keyboard-configuration
stops the layout switches for the session too. And here too they are back on reboot.

@Francesco (when you are back): I had asked Gerd what exactly he did, but didn't get a reply yet. He might be on holiday too. I believe he meant removing and re-adding the layouts in the gnome GUI as Frederik described.