Crash Report @ http://pastebin.com/ZmcmvgaB

When creating a new world, when going to actually joining it, everything works aok untill AbyssalCraft is added in then the above crash occurs when trying to join the actual world.

That's caused by a mod failing to register their EnumCreatureType(s) correctly (same as #81 and #88).
I recommend you take out mods until it stops crashing, then show the author of the culprit mod this: TeamLapen/Vampirism#64 (comment)