So you would want to check the server where Reporting Services is installed for a dump file that was already created and try to get more information from there.
Did this ever work correctly? Was the ReportServer database restored recently? Would/Did anyone manually update any of the tables?
Has anything changed with the login you use to connect to Reporting Services?
A couple of other things to check off the top of my head:
Check the keys table in the ReportServer database and make sure you have just one for this server/machine name and instance combination. There is typically another one with NULL for machine name.
Check the subscriptions table to make sure your subscriptions map back to a valid user in the Users table - OwnerID in the subscription table maps to UserID in the Users table.
Sue