A Project Professional 2007 user recently encountered the error message “The resource list is too long.  A resource list that contains more than 256 characters cannot be edited or deleted or used on the To line of a message.  Use the Resource Information dialog box to edit long resource names”.  Originally it was thought this was a limitation as to the number of resources that could be assigned to the same task.  Upon further investigation it appears as though it’s simply related to attempting to use the To Line (in the diagram below) to edit the resource names.  Since we’re in an enterprise environment we do not want to edit the resource names anyway, so this was a non-issue.  I suspect in a standard environment one should navigate to the Resource Sheet and edit the resource names there.