On Ubuntu you may have noticed that when running Picasa in fullscreen mode and returning you would notice the titlebar will be missing on the picasa. Normally this can be fixed after closing and re-opening picasa again.
But there’s a simple fix for that, Simply Unmaximize picasa. This can be done by right clicking on the titlebar and choosing Unmaximize. Resize picasa manually to fit your screen and you will not loose your title bar again.