An I/O error occurred when trying to read data from disk and send it to an agent. Examples:
An error of some kind has occurred when trying to send file data to an agent. The error message contains additional details to help diagnose the problem. For example, if the error occurred during the read-from-disk portion of the operation, the message states "error reading ...", specifying the name of the file emake was reading from and the OS error message for the failed read. If the error occurred during the write-to-network portion of the operation, the message states "error writing ...", specifying the type of exception that occurred and the OS error message for the failed write.
The list of possible causes for this error is virtually limitless: hardware failure; network connectivity problems; etc. Read the OS error message to determine the specific cause of the failure.
This is truly an example of an "exceptional" error - one that in practice, should not be expected to occur at all. Most likely if it happens once, it will not happen again, so a retry may be all that is in order. If the messages are occurring persistently, refer to the specific error message from the OS and reason about what could cause that type of failure. Searching for the OS error message using Google may turn up some clues.