You're right, what a strange situation. I would report this as a bug at the MSDN Feedback centre (https://connect.microsoft.com/feedback/). Anything reported here gets through to the development team. If this is a blocking issue you can report it to Product Support and investigation will be escalated and maybe a patch would be created.
In the mean time, as a workaround, you can manually repopulate the fields from the NewValues collection; it's not a great solution, but would allow you to keep working.
Alternatively, don't set the title text, but maybe have a label outside of the DetailsView that you update with error/warning messages. Or you could tempalte all of your fields and add a field alongside, to the right.
Dave