Can you please let us know if the account that you are using, and the other user's account both belong to the Administrators role? The exception indicates that there might be a reference missing - it could either occur if the required assembly is missing, or there is a permissions conflict. Are both users accessing the same project, or you are working on a dev/staging environment while the user experiencing the issues is accessing a deployed copy of the project? Looking forwards to your reply.
the Telerik team
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