I've tried this now on two different machines on two different networks. It may have to do with something I've got in Firefox though, I understand that. Not sure if anyone else is seeing this?
When I set up a mailing, under the "Trackable Links" tab, at the bottom when I go to set the drop downs, in Firefox 40.0.2 the drop down won't let me select them. In IE it works fine. All other web sites appear to be working fine with the Firefox drop downs. I'm not sure if it's a problem with Firefox and/or one of the add-ons, or if it's a problem with OpenEmm at this point... will look into it more.