We spent quite a lot time researching for a possible explanation for the error but we are not able to determine the root cause. This is why it would be really helpful if you can send us the whole project including a backup of the database so we could test it locally. Also, do not forget to send us all user controls, scripts, images, .css files, .dll files, etc. You can open a new support thread and attach the project as a zip file.
Looking forward to hearing from you.
the Telerik team