If you try to run the Workspace on a client that belongs to a different domain, there will be an alert 'CrossDomainError'. The 'CrossDomain' error message usually means that Workspace is unable to access CAS. It probably attempts to reach CAS by the internal address, you should change this address to the external one.
The same is for the thumbnail service – you should change its server name accordingly in the CAS configuration file, and the Media URL in CAM settings.