First nvision report in report book errors out

A few weeks ago we started having a strange problem where the first report in one of our nightly report books errors out with a message that it can't access the output file.  The next dozen reports in the report book all go to the same folder and run just fine.  There is a second report book that runs an hour later that includes many of the same nVision reports as the earlier book, and they all run successfully as well.  It's almost as if the connection to the output location times out, and the first report in the first