Project Server 2010 Beta: “Failed to provision site PWA with error”

I've installed Project Server 2010 Beta on my SharePoint 2010 Beta server and got this error when provisioning the PWA site:

Failed to provision site PWA with error: Microsoft.SharePoint.SPException: The template you have chosen is invalid or cannot be found. ---> System.Runtime.InteropServices.COMException (0x81071E44): 0x81071e44The template you have chosen is invalid or cannot be found.
at Microsoft.SharePoint.Library.SPRequestInternalClass.ApplyWebTemplate(String bstrUrl, String bstrWebTemplateContent, String& bstrWebTemplate, Int32& plWebTemplateId)
at Microsoft.SharePoint.Library.SPRequest.ApplyWebTemplate(String bstrUrl, String bstrWebTemplateContent, String& bstrWebTemplate, Int32& plWebTemplateId)
--- End of inner exception stack trace ---
at Microsoft.SharePoint.SPGlobal.HandleComException(COMException comEx)
[...]

The solution turned out to be simple: Just wait. Seems like there is an additional Timer Job for provisioning site templates and stuff. No idea when it runs as I had a weekend between failure and success, but it works now.