This message is basically a diagnostic from the SCSI driver. It can appear on the console every 10 minutes or so.
To reduce the frequency of this message, add this line near the bottom of the /etc/system file and reboot:
set esp:esp_use_poll_loop=0 |
You might also see this message repeatedly after manually removing a CD when it was busy. Do not do this! To return the system to normal, reboot the system with the -r (reconfigure) option.