I was really impressed by the new BCS stuff which I saw @ SPC2010. Offcourse, after installing the beta on my laptop, I wanted to test it out myself. So I downloaded SharePoint designer (which is pretty damn nice compared to the old one), connected to my newly created SharePoint site and clicked “External Content Types”.
Unexpectedly, this didn’t result in a fancy BCS screen, but gave me an error: “BDC Metadata Store is Currently Unavailable”. After some research, I found the following post on MSDN: http://social.technet.microsoft.com/Forums/en-US/sharepoint2010customization/thread/c9deb39e-d3c3-4102-a777-24a6dfed1701/?prof=required. The first fixes in there didn’t do the trick for me though. We tried analysing the results with Fiddler and found out that authorization was probabaly the cause of it, since the webservice requests were denied and followed by 302 redirects to the logon page of SharePoint.
I had my site setup with claims based authentication. I created a new site based on classic mode authentication and voila: it started working! It seems there’s a bug in SPD related to claims based sites, it also seems that this bug is already fixed in later releases, as posted by TAP members in the above forum post. So if all is well: this won’t be a problem any more in the RTM versions.