I am not quite sure what may cause the problem you experience and I need to examine your particular project. For the time being I can only make assumptions. I think that the problem may be caused by incorrect or missing databinding. I also recommend testing the project without the UpdatePanel and trying to detect whether the ajax request is causing the issue.
For your convenience I send you a sample example of the desired functionality - you can find it in the attached archive file.
In case you still experience problems with the implementation, please, open a new support ticket and send us a sample, fully running project (including a database) with detailed explanation of the information that should be displayed and we will modify it in order to meet your requirements.
the Telerik team