Hi, Has anyone seen the following problem? The Exchange 2007 Server occasionally generates the error (in the subject heading of this post) when a user tries to cancel one occurrence of a recurring appointment. If the user (account on which the error is being generated) were to be moved back to the Exchange 2000 server, this error goes away. Is there a way to fix this issue in Exchange 2007. Any help is greatly appreicated. Thanks in advance for all your help.