At jobs will fail with this error reported in the event log, and checking properties of events listed under "Scheduled Tasks" will also produce this error. None of the events will fire properly when they are supposed to.
This problem is caused by incorrect and/or corrupt cryptographic entries used by the service. To correct the situation delete any files found in the following folder:
c:\Documents and Settings\All Users\Application Data\Microsoft\Crypto\RSA\S-1-5-18
The next time a job is accessed, new (valid) cryptographic files will be generated and it will run as it should.
"Object already exists" error with Task Scheduler.
Moderator: jasonb