It might help to look at http://www.grainge.org/pages/authoring/rh8/using_rh8.htm #21 30- Dec - 2009. I'm trying to figure out a similar issue, though not identical. If you resolve your issue, please explain how in a follow up post.
Thanks for your idea. I read through the article you suggested and it does sound like a very similar issue. However, the small project I'm troubleshooting doesn't have an index.
Good luck with your own issue - I hope you find a resolution.
In the event the check in function failed, RH8 displays a dialog asking whether I want to leave or replace the local topic from RoboSource. I have found that using the Merge button has resolved the issue so that the project remains active and the link is repaired.