Closed 2.5.4: Trying to join my world but it keep getting me back to the main manu

[Heffalump]

Version:
2.5.4

What is the bug:
as I said in the title, it keep getting me back to the main menu.

PasteBin: http://pastebin.com/9H6WQMtn
in the crash report there was a lot of "\u0000" but I couldnt include that in the pastebin because I dont a pro user.

pic of it: https://gyazo.com/1afb8ab8112feb35b9598f61741c8d5b

Thx for help BTW

Mod & Version:


Paste.feed-the-beast.com log:


Can it be repeated:


Known Fix:

 

[UniZero]

Backup your world and delete the simple achievements folder from your save.

 

[Heffalump]

Backup your world and delete the simple achievements folder from your save.

thx a lot!

 

[UniZero]

thx a lot!

You are welcome.