deinstall the hildon desktop:

you can:
go to xterm
sudo gainroot

1. apt-get install --reinstall hildon-desktop
or
2.apt-get upgrade

he will ask to upgrade to the old version of hildon-desktop
say YES
and be happy!



and by saying lock in portrait mode, i mean, "keep the screen always in portrait, always in vertical oriented, even when it is in horizontal oriented"