NDPS printer not connected on multi-homed server

Weird thing here. NDPS printer is configured for LPR printing on a multi-homed server (corporate and private LANs). Most NDPS printers are on the private side, but this one is on the corporate side. Server can ping the IP for the printer, but it won't connect in the NDPS Manager when you start up the printer. If I change it to a printer name instead of an IP, it'll go to Idle, but nothing will print. With an IP, it's an immediate connection failure. It had been working fine for months until last week. Nothing has changed on the server to my knowledge, and the server's been up for 90 days. The Windows print server that also services this printer works fine, we just have it configured for NDPS for a legacy Netware-dependent app. I'm stumped.