Preview 4 is available for download. It should fix the 'An item with the same key has already been added' error!
If you have a problem please let me know what you were doing and attach your sharepod.log file.
EDIT: Preview4 has been re-released to fix a stupid bug added just before release. Please download the zip file again. In the readme, it will say Preview 4 - 4 September instead of 3 September.