Yet another worthless error dialog
Category WTF Technical Lotus Bitching
<bitch type="driveby" reason="errorDialog" >

So I'm working in designer, and changed the properties of a table cell. It previously had a graphic image assigned as the background, which I replaced with a graduated color change. Upon saving, I received this incredibly helpful error message.
Good thing it explained what the problem was and what to do about it, otherwise I might have been confused.