There was a failure executing the receive pipeline. Reason: The pipeline component ... can not be found. If the component name is fully qualified, this error may occur because the pipeline component can not be found in the assembly.
DLL is in GAC for sure. Hosts were restarted. Any ideas?
When Windows looks for a DLL in the GAC, it matches on three things, the fully qualified name, the version number and the public key of key used to sign it. If any of those three don't match, it will throw that sort of error. Double check that the version in your pipeline is the correct version.