[galaxy-dev] What's causing this error?

Hi, Recently I moved my locally installed Galaxy from a local hard drive to an NFS mounted hard drive, when I run some tools, I go the following error from the log file: Job output not returned by PBS: the output datasets were deleted while the job was running, the job was manually dequeued or there was a cluster error. I am pretty sure the job was not manually dequeued. Any idea how this happened and how this can be fixed? Thanks, Luobin