It's probably because the addon is using an old version of libAddonMenu 1.0.
Download the newest version (r10) of LAM 1.0 here:
https://www.dropbox.com/s/47nx7zoitb...nu-1.0-r10.zip
Exchange the "LibAddonMenu-1.0" folder with the one from the new downloaded ZIP file above, inside the "ThurisazGuildInfo" addon's folder, and do a /reloadui ingame.
I hope this fixes your problem.