Had the same problem. It seems like it is a generic error for what could be a multitude of problems. Your best bet to identify and resolve the problem is to host the Customer Portal on your on IIS server and use Windows Server 'Event Viewer' and check "Windows
Logs > Application" for errors.
My problem lay in the Authentication settings of the web.config file. Specifically I failed to add in the web.config:
<certificateValidation
certificateValidationMode="None"/>
Within the web.config section referenced below. This was documented in the associated documentation "Portal Configuration Guide - Windows Azure ACS Authentication.doc"
<configSections>
<section
name="microsoft.identityModel"
type="Microsoft.IdentityModel.Configuration.MicrosoftIdentityModelSection, Microsoft.IdentityModel, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/>
</configSections>
<appSettings>
<add
key="FederationMetadataLocation"
value="[WS-Federation Metadata]s"/>
</appSettings>
<microsoft.identityModel>
<service>
<audienceUris>
<add
value="[Realm URI]"/>
</audienceUris>
<federatedAuthentication>
<wsFederation
passiveRedirectEnabled="false"
issuer="https://[Service Namespace].accesscontrol.windows.net/v2/wsfederation"
realm="[Realm URI]”
requireHttps="true"/>
<cookieHandler
requireSsl="false"/>
</federatedAuthentication>
<issuerNameRegistry
type="Microsoft.IdentityModel.Tokens.ConfigurationBasedIssuerNameRegistry,
Microsoft.IdentityModel, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35">
<trustedIssuers>
<add
thumbprint="[Thumbprint]"
name="https://[Service Namespace].accesscontrol.windows.net/v2/wsfederation"/>
</trustedIssuers>
</issuerNameRegistry>
<certificateValidation
certificateValidationMode="None"/>
</service>
</microsoft.identityModel>
</configuration>
