This error refers to one of the agent's activities as described here and means that it requires some more time to do the operation. The error is intermittent and does not necessarily mean something critical. Agent can restore itself from this state. Depending on the operation mentioned in the error message, admin can identify the narrow place in job execution. This may be clogged disk, script execution, availability of files themselves.
If the error does not go away within reasonable time, it's better to contact support with some details about the job.