Can't open Office documents in Office 2010 client from SharePoint

I have installed SharePoint 2010 beta Standalone on Win Ser 2008 R2 and everything is working pretty well apart from the fact that I can't open Microsoft Office documents using Office 2010 Release Candidate (or beta) 32-bit or 64-bit. I can open them using Office 2007, just not Office 2010! The only error Word or Excel displays is "Could not open "http://myserver//mysite/mylibrary/mydocument"

This is driving me nuts! I have the Office Web Apps installed and editing in the browser works fine. I just can't open them in Office proper!