Rep2 displays a message which shows how much reputation you gained, and how much is needed until the next standing, including fallover rep to secondary factions.
Fubar - FactionsFu and Rep2 don't seem to play well together. If you have FactionsFu, disabling it should make Rep2 work again. If not, try downloading the newest Ace2 libraries
http://wow.curse.com/downloads/wow-addons/details/ace2.aspx and replace the ones in the Rep2/Libs folder with the new ones.
I updated the libraries first which worked with a soft reload of the UI but once I exited and reentered the game it broke again and that's when I narrowed it down to FactionsFu. So it may or may not be necessary to update the libraries.
http://wow.curse.com/downloads/wow-addons/details/ace2.aspx
and replace the ones in the Rep2/Libs folder with the new ones.
I updated the libraries first which worked with a soft reload of the UI but once I exited and reentered the game it broke again and that's when I narrowed it down to FactionsFu. So it may or may not be necessary to update the libraries.