Per the post above, I experimented trying to export smaller numbers of contacts. I had about 800 total contacts, and thought perhaps that was too many to export at once. So I started exporting smaller chunks of contacts, and what I discovered is that the problem wasn't the quantity of contacts -- the problem appears to be that certain contacts just won't export. And if one of these problem child contacts is included in the export group, then the entire group won't export and you get the "Unable to Export vCard" error. Unfortunately I can't find a common characteristic that makes a certain contact a problem child. So the only way I could find them is by trial & error. I would select 50 or 100 contacts and try to export them to vCard. Most groups exported without a problem. But if I received the error, I would just keep selecting smaller & smaller subsets of that group until I found the problem child. A problem child will not export even as a single record. Once I found one, I did a manual copy of all the info in that contact record, pasted it to a text file, and then deleted that contact. Once I deleted that contact, then the entire original group of 50 or 100 records would export just fine (unless there was another problem child in there).
Out about approx 800 contacts, I ended up with just 6 problem children. Once I deleted all 6, then I was able to Select All and export all contacts. It's a pain, but ultimately it took probably 15 minutes to blast through all contacts and find the problems. Not an elegant solution, but hopefully it's helpful to others. Would love to hear if anyone else has the same experience, and if you can see any pattern in what causes a record to be a problem child.
