Changing IIS User Breaks Authentication

[Heather27]

When I change the user IIS runs under, the Vault logins stop working.

I'm using identity impersonation to connect to the SQL Server, and it connects to the SQL Server, and the VaultService Web Service definition page displays properly, but it says the username and password are invalid when using the Vault Client.

If I change back to the old user, it is fine. I checked that the new user had the access outlined in the Installation Tutorial:
* the local directory containing the server installation files (by default, InetPub\wwwroot\VaultService).
* the directory where the log files are written (by default, WINNT\Temp). The log file location can be changed after installation, in the Vault Admin Tool under Server Options.
* the IIS process account's %userprofile%\Application Data \Microsoft\Crypto\RSA\MachineKeys or to %ALLUSERSPROFILE%\Application Data\Microsoft\Crypto\RSA\MachineKeys if the IIS process account does not have a user profile.
* the Vault Shadow Folder directory.
* Windows\Microsoft.NET\Framework\<version>\Temporary ASP.NET Files.

It's almost like the password encryption is broken...

Update: Changed the user to be a db_owner of the SGVault database, and the problem was fixed.