Found the issue in case anyone runs into the same problem. The problem isnt so much with Deluge as it is specifically Google Chrome. The latest Chrome update breaks the window in question for some unknown reason.

In the last 24h or so my installation of Deluge no longer allows me to select the Files or Options tabs when adding new torrent files, and thus no new torrents can be added. I've made no changes or updates for weeks so this is rather unexpected and I can't seem to find any reference to why this is s...