Problem: I import a step file. It opens fine. I save it as a Solidworks part or assembly. I save and close the file. When I re-open the file, all of the parts are greyed out. Then I get an error message "An error was encountered while trying to open your file."
The only way to avoid the problem is to recognize the features and convert it into a Solidworks part and/or assembly. Not really a big deal until I get a large assembly. Then I just save the large assembly as a Solidworks part file. Unfortunately, that limits any editing of the assembly.
This also happens with iges files as well. Parasolids do not cause the problem. Not sure about other file types. Doubt that it's a corrupted file, because it happens from multiple file sources. Been havings this problem since 2013 release.