Cannot select certain authors for posts after import

I found the issue, thanks to @Toscho giving me the spark of an idea. We are using custom user roles and capabilities. It had something to do with the User Role Editor plugin. Deleted the custom role, and created a new one, reassigning all capabilities. Then updating all users to the newly created user role. Problem fixed.

Not sure why that happened, but for anyone else who may use this plugin or run into this issue, this is a fix that worked for me.