No, I checked all that.
Somehow, the problem fixed itself. I want through and examined each project, ensuring that files went where they were supposed to, then went and recompiled several other related dll's not in this workspace, and then rebuilt the whole mess. I still don't know what the actual cause was, probably a corrupted or out-of-date .lib file somewhere.
There's definitely something amiss in the LabWindows 2013 linker or make routine somewhere. Several times now, I've noted that if I close a project or workspace and open another one without closing LabWindows that when I build the new project files from the old one appear in the build output window, dragged in somehow. I'll see if I can nail down an example.