Hey there,
We have a Sharp AR-M162 printer and sometimes find a similar problem.
From what I have found it indicates a network connectivity error. I haven't found much rhyme or reason for this error - it is an annoying intermittent issue.
Usually turning the copier on and off fixes it temporarily, but it does sometimes come back.
We find it seems to happen if someone hasn't scanned for awhile - it's as if the scanner part can't figure out where to send the file.
Have you made any progress on this issue?
ITfromZX81