Well, I had a previous version of NASNav that gave this problem, which I uninstalled and then replaced with 2.63, which gave the same problem, but I suppose that it wouldn't hurt to do it again. (I don't have that machine in my possession right now, so it may take a couple of days.) Thanks.
(Do you have an idea of just where the problem is manifesting? Is the NASNav installation supposed to specify some browser to open the address, or maybe to stick an .html to it, or something like that?)
(I just opened the old NASNav2, v2.43, on my desktop computer, and I see that the pop-up menu item that corresponds to the new "Settings" is "Open web setting", not "Web access", as I mis-remembered in my original post. Sorry. I know now that "Web access" is something completely different.)