By targeting, do you mean using a left-click with the mouse, or also a command like /target ... (/target next {player|item|npc})?
Configuration of controls and shortcuts are stored in %APPDATA%\PlaneShift\options under Windows (shortcutcommands_character.xml and controls_character.xml). I wonder if you managed to mis-configure your left-click behaviour. But it may also depend on the feedback from your OpenGL graphic driver.
Most interesting, doors are no "items" to target, they are only "action locations" which should not be targetable at all for a normal player (you can only call a context menu on them using a right-click, usually).