All non-vanilla blocks disapeared on server

[Voho]

Me and a close friend have been playing on a private server for the past few days, and we have a large stockpile of items stored in lockers. However, this afternoon (everything was fine earlier) we encountered some error messages related to entities, which can be found in this pastebin:

http://pastebin.com/HeWdc41E

Now every single non-vanilla block (as far as I've seen) is missing, including all of our items within lockers.

Please, how can we recover all of our progress and loot?!

[SirBeruss]

It looks like it's not just Hexxit either. Other big mods do it to, Including B-Team. It only happens when I'm trying to run a private server for me and my friends using Hamachi. Also some of the OPs options are gone too. But in single player, everything works as it should.