We haven't experienced this problem. In your case, it may just be that the port was disabled, and defining an IP address enabled it. If this problem occurs again, check the status of the port via the printer's control panel; take the printer offline, select the Input Port menu, then select Ethernet and check if it's enabled/disabled. Again, from our experience the following statement on page 2-1 of the "Network Installation and Configuration Manual" is true:
"If you are ABSOLUTELY sure that NO host on the network uses (and never will use) the TCP protocol, an IP address is not needed."
To set the netmask to 255.255.252.0, you can do this via RCF (the printers Remote Console Facility) with the following command:
define server subnet mask 255.255.252.0
NOTE: You must be in super user mode to execute this command. After getting into RCF with "access" as the default password, you can get into super user mode by typing su <cr>, and then the super user password which is "system".
Changes will take effect after the printer has been restarted.