Mojang is planning to release Minecraft 1.7.6 tomorrow. However, this new version won't allow you to connect to the server: you need to stay with us on versions 1.7.2, 1.7.4 or 1.7.5. Make sure to select the correct option in the Minecraft launcher!
As I've posted before, 1.7.6 is the release preparing for username changes. Since many modifications are needed server-side, from both me and mod makers, we won't be updating to that version for a while still.
UPDATE: Minecraft 1.7.7 has been released to fix some bugs. The comments above still apply.