problem subscribing reports

Hi all

I'm trying to subscribe to some reports from web portal --> settings --> subscriptions,  but as I press the button "Add Subscription", I get the following error message:

"Error while loading the collection RPSReport in VI_MyData_PersonalData_RPSControlRef2.

Could not load file or assembly 'rps.customizer' or one of its dependencies. The system cannot find the file specified'

Please can someone advice me about what to do in order to fix this problem?

Thanks in advance

Alberto