If you notices these errors
// mental ray for Maya: using rayhosts file C:/Users/User/Documents/maya//maya.rayhosts
// Error: (mental ray) : Unable to load file: plugin.dll //
// Error: (mental ray) : cannot load plugin.dll, The specified module could not be found. //
using Mental Ray Satellites, probably the slaves don't have the plugin installed. A quick fix, if you don't need the plugin for the scene:
run Window -> Rendering Editors > mental ray > Shader Manager and unload the plugin:
Best regards.
