Recently I ran into a problem with our Commerce Server installation on our internal and external staging/UAT environments, when we tried to verify the property on the User Object definition we were presented with a "The webpage cannot be found" message. Turns out Commerce Server installs a "widgets" virtual directory in your root application. If you don't have a root application or have it switched off you can follow the instruction here substituting the new Commerce Server path (C:\Program Files (x86)\Commerce Server 11\Widgets) for the old Microsoft one. If you want to specify a different location for the widget directory (our staging instance is also running a staging instance of Sharepoint in the default application) you can follow the instructions here to get Commerce Server to look elsewhere. Unfortunately you need to do this on each definition and as a note, don't include the http:// in your <server name> value.