I just updated to the Q1 2011 release, and I ran into a new bug with invisible columns. If I add a couple columns with their Width property set and IsVisible = false, followed by some visible columns, the invisible columns appear as a gap in the grid (1st attachment). If I make those columns visible and then invisible again, then the layout appears correctly (2nd and 3rd attachments). My real scenario is more complicated than this, but this was the simplest way I could reproduce the bug.