Over time when playing Wurm Unlimited, my Target Window disappears, Quickbar disappears, Select Bar disappears, and Skill Tracker Window loses yellow color randomly. Relogging fixes it temporarily but eventually it always comes back and there doesn't seem to be a way to fix it.
http://images.akamai.steamusercontent.com/ugc/257093625784492359/DAF9D812FD3FC618D0874F11F84671EA6EF9BEDF/
The pic doesn't have the target window disappearing, but it eventually does like the Select bar and Quickbar.