I think the 1.2.5 jar that I tried connecting to the PvP server with was somehow partially updated.

Basically, get that Minecraft Version Changer (MVC) (it's VERY easy to use).

If you want to play the pvp server, change to 1.2.5.

If you want to play the main server, change to 1.3.1.

This should resolve the problem.

When will the PvP server be updated to 1.3.1 by the way?

Just out of curiosity.

Soon

Derp.

75% of jallaf's posts are "Soon".

Welcome to the hype train ..