For those of you foolhardy enough to be running Vista x64 (myself included!), VS 2008, and the latest build of the ADO.NET Entities framework… you may well hit the following error message:
The specified metadata path is not valid. A valid path must be either an existing directory, an existing file with extension ‘.csdl’, ‘.ssdl’, or ‘.msl’, or a URI that identifies an embedded resource.The catch is that apparently the designers are not supported on 64-bit machines. The workaround is to copy two files from %windir%Microsoft.NETFramework64v3.5 to %windir%Microsoft.NETFrameworkv3.5:
then restart Visual Studio and rebuild your solution.
Thanks to Tommy Williams @ MSFT (found on the forums)