Im running server version 1.7.1 and I set my client to also run experimental versions (1.7.1). When I go into my server list my server which is running 1.7.1 has a red x through it and says 1.7.1. If I hover over it, it says server out of date.
I found that refreshing repeatedly will sometimes get it to go away temporarily.
Is this still a concern in the latest Minecraft version 13w48b? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.