I've been encrypting and decrypting files and folder using nautilus and the seahorse-plugins package for the past few Ubuntu releases. It appears that seahorse-plugins is no longer available in oneiric's repos: see here, and here.
Looking a bit further there is this bug report #796752 on Launchpad which seems to lay the blame on the transition to Gnome 3. Looks like it might be available in Precise.
Looking a bit further there is this bug report #796752 on Launchpad which seems to lay the blame on the transition to Gnome 3. Looks like it might be available in Precise.