Yes, that did it - the URL should have "GRid" before the number, but it was changed to "grid" and that screwed it up. When I went into the URL on the "memorial not found" page and manually changed it, the right memorial came up.
But here is the puzzling part - when I click through from the "sources" specifically for the death event, it shows the URL for the memorial as I originally entered it, and it works. So the problem is with how the system is picking up the URL to create the "new" link on the profile sidebar.
I can't begin to imagine how they would have set things up so that it actually changes a URL - that's about the dumbest thing I ever heard. Thanks, however, for coming up with the "what" part of the issue, now we just need to know "why" and "how," and what they are going to do to fix it.
Edit: I have sent a message to tech support, with a link to this thread since it's all spelled out here (including BB's experience with the same problem but a different source).