I suppose the part was created inplace from the assembly. In that case all visibility modifications belongs to the top-level assembly's design view. For example if I create an assembly and inplace create a part, add some work geometries and make some of them invisible. The visibility of part\work geometry is recorded to the assembly's DV. If we place another instance of the part all work geometries will be visible because we set the visibility of the first part instance's workgeometries.
If you want to control the visibility of the part definition, it is necessary to open it standalone (not inplace).
Thanks,
Csaba
THAT'S IT....!! But I would like to add that the only time I had actually had to utilitze this method is with created work planes, but not all of them. All other aspects of the created part's features and their visibilites don't have to be controlled in a stand-alone manner.