SSRS Subscription Error: "Failure sending mail: Report processing has been canceled by the user. Mail will not be resent."

On the report Subscriptions page, under "Status" for Last Run, it has the following error: > Failure sending mail: Report processing has been canceled by the user. Mail will not be resent. It's a subscription, no **person** canceled this. Maybe there is a problem with a service. I can run the report fine right now. The only log I can find is here: > C:\Program Files\Microsoft SQL Server\MSRS10_50.MSSQLSERVER\Reporting Services\LogFiles There are two lines for the report: > notification!WindowsService_508!d24!02/10/2014-05:45:05:: i INFO: Handling subscription 75b94483-618d-4463-b6c0-90916b92cb6 to report ReportName, owner: domain\user, delivery extension: Report Server Email. > library!WindowsService_508!d24!02/10/2014-05:45:05:: i INFO: RenderForNewSession('/Reports/ReportName') These lines don't indicate an error occured. I've been looking through all of the logs I could find and I can't find any sort of description as to what would have caused this. I would like to find out where this information is logged, so I can create a job that looks for messages like this to alert users of a failed report. I would also like to know where the logs are in case I do need to troubleshoot something vague like this. I really would appreciate any help :)