We recently set up a one-way trust between two domains. Some admins however were unable to make RDP connections to the servers in the trusting domain even though they were in a group that was part of the administrators group on the local servers. After providing login credentials to domain A, they'd get authenticated and begin to login to comptuters in domain B only to get this error:
Logon Failure: The machine you are logging onto is protected by an authentication firewall. The specified account is not allowed to authenticate to the machine
This error is occuring because we set up a "selective authentication" when we created our one-way trust. We did that deliberately as we wanted to do just that and selectively allow access to resources in domain B. Here's the fix...
That should get you going!