I've noticed a lot of problems cropping up with the plugin especially relating to template_tags. This is partly because of how coauthors are stored. Long story short, each post has one main author associated with it, with other coauthors stored in custom fields. This isn't really the best approach to storing them.
As such, I will be re-architecting the entire plugin to take a slightly different approach on how authors are stored. As well, I will ensure that the new version will be localization-friendly; the current one is not. And I will do my best to allow for a graceful upgrade path.
Depending on how much other life constraints get in the way, I will be releasing this in the next few weeks.