Two-way domain trusts required
Claims-based authentication between trusted domains requires two-way domain trust. A one way domain trust will result in the following error message:
There was a problem accessing the site. Try to browse to the site again. If the problem persists, contact the administrator of this site and provide the reference number to identify the problem.
Reference number: <GUID>
For more information, see the following KB article An error message occurs in Microsoft Dynamics CRM 2011 when trying to access the CRM URL using a One-way Domain Trust