On that note then, I was looking into your D-link router. Great dual-band router, by the way. Ethernet may be trying to connect to a different subnet than the printer needs to communicate. I have a document for you to review as some steps have already been done. LAN (local area network means Ethernet) and this document also discusses the problems you are having with the second computer now.
I understand you have Windows 7, so this is simply a document I want you to read. I literally stumbled upon it right before I read in a previous post you had similar error messages after you restored the router. Usually once I reach page 4 of troubleshooting I can forget what has or has not been done yet and that is why I am taking time to re-evaluate the situation before offering any suggestions. Once again, your patience is greatly appreciated!!