Gee, that's a good one. I don't have an exact answer, but I think it is a configuration issue, rather than anything actually broken. Keep in mind that IP ports are not really hardware ports at all, but software addresses within a communication protocol. So there is nothing to "break" (as far as I know) at one port versus another.
You might try switching the port back to 1352 and see if it works now. Maybe it was not really the problem, but something else was going wrong with replication.
You might also try looking at Domino R5 Admin Help / Index / Port. There are lots of entries there about setting up port addresses, so you might find something there that applies to your setup.
This was first published in May 2003