I have long been annoyed by a tendency of Dreamweaver to forget my panel/palette layout between launches -- not just MX but previous versions (all Mac OS). I think I see why now... it depends on whether DW is in the foreground when it quits. If it is then all panels etc. are visible; but if DW quits in the background, while these elements are hidden, well, logically enough in a stupid sort of way, it appears that this is what DW "remembers"! How can you quit DW while it is in the background? Easy -- bring any other app to the fore then quit DW from the Dock (OS X obviously). This probably holds true when logging out or shutting down, though I haven't put that to the test (got better things to do!)

I suppose its too much to hope that Macromedia will fix this long-standing bug, but in the meantime I will try to remember to only quit DW from within the app.