Weird invisible link

When I tell my file to link to files on startup it tells me that it can't find one of the links (it is fine with the others) and that the link is this ungodly long path to Dropbox to files at a company where I worked 12 years ago.  I get that I must have at some point used a template file that caused this problem, and it happens from time to time.  I get past it by clicking through and move on, but it's a pain, and a little creepy.

So here's the problem - when I go to edit links it of course doesn't show.  How can I get rid of this?