OK - I probably shouldn't have TRIED doing what I did, but none the less - I think it's a bug.
I had visited someone else's waymark a couple days ago. Tonight I was going through my GPS receiver deleting some of the waypoints I no longer need. I happened to reference my visit log from a couple days ago verifying that I had put the better coordinates in my log. I saw that I must have entered the northing coordinates for both the north coords as well as the west coords. I clicked on 'Edit Visit/Comment'. Of course, I got the 'Once a log has been in the system for 24 hours it can no longer be edited (but can still be archived).' message. But I clicked on the 'Update Visit' button anyway hoping that perhaps I could fix the additional coordinates that I had entered. Well, this ended up zeroing out the additional coordinates that I had entered, so now my visit log shows '00° 00.000 000° 00.000' for the additional coordinates in my visit log. I think clicking on it once zeroed out either the north OR the west coordinate, but not both, however, I clicked the 'Update Visit' button a second time which zeroed out the other. I still see the '00° 00.000 000° 00.000' when I go back and look at my visit log. The URL for the visit log is http://www.waymarking.com/logs/details.aspx?f=1&guid=1b238d48-a78c-4df0-b6f2-f5db763da1df
It's not really too much of a big deal, but something that I'm sure is not intended.