Do you have the capability of booting into DOS? This would be to test the parallel port by doing a type filename > prn to test the combination of port, cable, and printer.

During boot does the printer do anything. IIRC there is something dumped to the port, possibly a carriage return.

Any problems showing in /usr/adm/messages ? This is a hardware record of things found during boot, with the last one being the latest boot.

Other than checking for something being set incorrectly in the BIOS I would remove the printer and parallel port, reboot, and reinstall. I've run out of ideas.