An input/output error occurred. This may signal incorrect handshaking protocol or improperly terminated or faulty cables.

I once got rid of an ioerror by cleaning up the hard disk of my RIP. Maybe this was a coincidence but it may also show that ioerrors can point to a lack of resources (RAM, swap space,...) on the PostScript RIP.

Offending command: random characters

If the offending command is just a series of random character, this may indicate a problem with the communication link; check your network, communication settings, disable spoolers or run the job again. You could also reinstall the printer driver because it may be corrupted.