If you are meshing an assembly, and one of the parts fails to mesh, open the part in its own window. Once you are able to mesh the part here, apply these mesh settings as Mesh Control in the assembly. Another, simpler method than the one just described is to apply mesh control to the failed component. In the Mesh Control property manager, you will find an option called "Use Per Part Size." This option will apply an appropriate mesh size as if the part was opened in its own window and meshed.