There is a bug in the SQL Server 2008 June CTP that causes Declarative Management to be inoperable. The fix is very simple. Launch a command line and run the following command:
C:\Program Files\Microsoft Visual Studio 8\SDK\v2.0\Bin\sn.exe -Vr Microsoft.SqlServer.DmfSqlClrWrapper,89845DCD8080CC91
After running the command you will need to restart the SQL Server service.
The Declarative Management DLL, which runs inside the SQLCLR, did not get signed as part of the build process. Running the above command will disable strong name verification for this assembly. Client-side checking of policies: "Test Policy" and "Run Now" will function as expected without the fix. Policy automation (enforce, check on change, and check on schedule), though, will require applying the above fix.