If there is any exception thrown by Sitefinity it will be stored in the Error.Log file. Because sometimes this file can be very big, you can delete it and try to reproduce the error again. If something wrong happened the file will be recreated and the error logged.
Additionally I would like to suggest you to submit a support ticket about this issue so we can investigate it in detail.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items