aspnet_regiis error when encrypting connectionStrings

I have a website whose domain is www.myWebsite.com and on my server it is located in a directory on my c: drive at the following physical path:

   c:\dirVirtual\myWebsite

I have a connection string defined in my web.config in the connectionString section.

<connectionStrings>

   <add name="myConnectionString" connectionString="Data Source = 1.2.3.4; Initial Catalog = XYZ; UserID=user;Passowrd=xyz" providername="System.Data.SqlClient" />

</connectionStrings>

I go to the c:\Windows\Microsoft.Net\FrameWork\2.050727 directory and there run the following command to try to encrypt this section:

aspnet_regiis -pe "connectionStrings" -app "/myWebsite" -prov DataProtectionConfigurationProvider

When I do this I get an error

Encrypting configuration section...
A configuration file cannot be created for the requested Configuration object.
Failed!

The -app parameter says it is supposed to be the virtual path but I'm not certain I have that correct. I don't know where to look to see what the virtual name is.

I have been able to successfully encrypt other websites on the same server. Is there any way to find out what the error really is?

Thanks,

Bob