I know that ppl have already asked questions regarding encrypting web.config.
im also trying to encrypt my test config file, but im getting this error.
aspnet_re
Take a look at this , see if you set it up correctly
http://msdn.microsoft.com/en-us/library/ms998283.aspx
A possibiliity is to specify the site with -site "SiteName" otherwise it will use the default web site.