There are two reason why a user would be unable to schedule reports in Information Manager.
1. The user is connected to the SMS server via a remote desktop or terminal server connection. Windows does not allow creation of scheduled tasks via these connections methods.
2. The user is logged in directly at the machine, but improper Windows login credentials have been supplied to Information Manager. To correct this, open Information Manager, go to File->Change Windows Account Info and supply a valid Windows Administrator login and password.