Michael I sent you a DM on the community with my email. I could validate this against my debug version if you can toss me one of those files that can reproduce the issue. I just want to make sure this isn't an issue when importing a large amount of users and this is a case we don't normally come across often and would like to make sure there are no problems at all with it. I can also help you out and make sure we get all those users imported. As Emily mentioned above, make sure you are on the latest first.
Matt Petty
Senior Software Developer
SmarterTools Inc.
www.smartertools.com