Same problem here. Fresh install on Mac OS X 10.6 (first time user). Deleting the settings didn't help either.
The problem only appears when the folder view is displayed (a folder or project is opened). There's reserved space for the tabs to display but they aren't shown. Also when I open several files from the folder view, it appears like each opened file would replace the previously opened one. (I can't switch between them via keyboard shortcuts. When closing one tab via cmd+w there's none left.)
Again, this problem only appears when the folder view on the left is displayed.