Hmm, things are getting odd! I don't see any errors when loading or editing my original part, it just doesn't display the text (which I'll work on). I thought maybe I had to import the exported part (which I hadn't done, my bad!) to get the error message but for me, when I deleted the part and imported it again it is just as happy as with the original, no error messages either on load to Fritzing or when I started the parts editor from the mine parts bin although the xml is obviously wrong (even I can see that once it was pointed out 
) Ah! late inspiration, deciding to be complete I re imported the part then moved it to the breadboard before starting parts editor. Now I get the error message from parts editor which I didn't (and still don't) when I edited from the mine parts bin. Any way, thanks, knowing what the problem is points me in the direction of a fix (either give up on silk screen text, which I don't want to, or figure out how to do it correctly!) and I learned to put the new part in a sketch to be sure it really works!
Peter Van Epp