LaserWriter Select 360 won't print - any idea why??

Hello Moe and other printer experts,
I have an Apple LaserWriter Select 360 that has suddely stopped printing from both Mac & PC. On the Mac I get error -50. The PC does all the dialogue box routine but nothing happens. Since the printer is connected by serial cable it can't be a cable issue.

The Mac 'sees' the printer through the chooser, and in setup bu twon't print to it.

Anyone have any ideas what could be causing this?? Thanks!