There are dozens of Usenet posts with this same error. There isn't anything on the error at Technet, so don't bother looking there!
From the other posts, people report that the full message from Event Viewer is similar to the following:
"The action to create the scheduled report, "Report Job", with the specified credentials, failed. The error code in the Data area of the event properties indicates the cause"
Now, this sounds to me (and to people on the Usenet) like a login/password account problem. When you set up the report in ISA, did you specify which user account the scheduled job would run as? The same type of thing when you use the Scheduled Job wizard to make a scheduled job; you have to specify what user account the job will run as, including the user name AND password.
Well, if this is the same problem in ISA, the first thing you should do is check the ISA schedule to run this report, and make sure it has the correct password for the user account it is set up to use. You can use either a domain account, or a local machine account.
Since ISA is running on a SMS server, then this machine is a domain controller. In this instance, the local accounts ARE domain accounts!
So, make sure the right password for whatever account you set it to use is entered in the password box. You won't be able to read the password, so just type in it again and save the ISA schedule.