This is a known conflict between the Serialport Arbitrator and PrintMonitor with the Personal LaserWriter LS. It occurs with system software version 7.0 or 7.0.1, and with the Personal LaserWriter LS driver version 7.0 or 7.1.
The only current workaround is to either disable background printing, or remove the Serialport Arbitrator, as you have already discovered.
Article Change History:
21 Nov 1994 - Reviewed for technical accuracy.
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