No Access to /XrmServices/2011/... using Organization in URL

I am having an issue with loading data in the CRM Email Router Configuration Manager in CRM 2011 UR 11.

I get this error:

"Metadata contains a reference that cannot be resolved:  'http://<server>/<organization>/XRMServices/2011/Organization.svc?wsdl'."

Attempting to browse to these URLs (we have two organizations) produces a 404 File Not Found error in the browser.

If I remove the organization bits from the URL, the web service loads in the browser:

'http://<server>/XRMServices/2011/Organization.svc?wsdl'

Normal web access to CRM works fine using the organizations in the URL, but I get no joy with the web services.

Any ideas?