Open the Mac Finder, under devices, what is the name of the Macintosh Hard Drive?
try reseting the workspace layout:
go to Window -> Work Space layout -> Reset '<your layout name>'
and deleting the Dreamweaver Cache file from the users configuration folder:
alsop try disabling the preview, go to WebAssist -> Preferences in the preview section check the option to disable the preview. It will still be available if you click the preview place holder to open it in the browser.