I have a report scheduled in CRD that is running from the local hard drive. It ran successfully through the day yesterday, but then for about 5 hours during the night it failed, with a "file not found" error. Early this morning, without intervention, it began running successfully again.
I've been getting a very similar problem. Schedules will run without problems, and then later when I go and double check things in the schedules I get a "File not found" error... but then if I refresh the package, 'sometimes' it fixes it... no idea why this happens.