The laser's frequency has become unstable. This error may indicate that the laser beam has been momentarily reflected back to the source by some obstruction.
What you should do:
To clear the error, power the MP down.
Power the MP back up.
If the error reoccurs, take off the covers and check the status lights at the back of each laser to determine which laser is at fault.
If the error reoccurs, contact your Giddings & Lewis service representative.