FAST Seach – Admin OM Exception occurred. Message: Failed to communicate with the WCF service – The trust relationship between the primary domain and the trusted domain failed.

I was getting this error:

Admin OM Exception occurred. Message: Failed to communicate with the WCF service. , Error Code:e107, Stacktrace:Microsoft.SharePoint.Search.Extended.Administration.Common.AdminException: Failed to communicate with the WCF service. —> System.ServiceModel.FaultException`1[System.ServiceModel.ExceptionDetail]: The trust relationship between the primary domain and the trusted domain failed. 

This was a great blog to point me to the issue.  Turns out I had two domains in my Active Directory that had lost the trust setup but nothing was broken with my Active Directory or FAST setup.  I had to delete the trusts and add them back, then it started working again.

http://blog.isaacblum.com/tag/the-trust-relationship-between-the-primary-domain-and-the-trusted-domain-failed/

Enjoy!
Chris