Error: QDSMain.Exceptions.DistributionFailedException

[#1]

I'm using Enterprise Server V11 SR6.  Over the past two weeks have been encountering the following error message when running a delta load job.

The task "Reload of QVWs\L1\Extract Unisoft Sales.qvw" failed. Part of the log file follows:

11/6/2014 3:06:32 AM      Error       The Source Document was NOT reloaded successfully. DocumentPath=D:\QlikView\QVWs\L1\Extract Unisoft Sales.qvw.

11/6/2014 3:06:33 AM      Error       The task "Reload of QVWs\L1\Extract Unisoft Sales.qvw" failed. Exception:

1. QDSMain.Exceptions.DistributionFailedException: Distribute failed with errors to follow. ---> QDSMain.Exceptions.ReloadFailedException: Reload failed ---> QDSMain.Exceptions.LogBucketErrorException: The Source Document was NOT reloaded successfully. DocumentPath=D:\QlikView\QVWs\L1\Extract Unisoft Sales.qvw.

   at QDSMain.ReloadTask.VerifyConditions(TaskResult taskResult)

   at QDSMain.ReloadTask.Reload(String fileName, TaskResult taskResult, String sectionAccessUserName, String sectionAccessPassword, eReloadOptions reloadOption, String variableName, String variableValue, Boolean moniterCpuUsage)

   --- End of inner exception stack trace ---

   at QDSMain.ReloadTask.Reload(String fileName, TaskResult taskResult, String sectionAccessUserName, String sectionAccessPassword, eReloadOptions reloadOption, String variableName, String variableValue, Boolean moniterCpuUsage)

   at QDSMain.DistributeTask.Execute(TaskResult currentTaskResult)

   --- End of inner exception stack trace ---

   at QDSMain.DistributeTask.Execute(TaskResult currentTaskResult)

   at QDSMain.Task.AbstractTask.TaskExecution(ILogBucket logBucket, TaskResult taskResult)

Attached is the full error message.