It keeps crashing when i want to type a word or something

---- Minecraft Crash Report ----
// You should try our sister game, Minceraft!

Time: 7/10/13 2:42 PM
Description: Ticking tile entity

java.lang.ClassCastException: asj cannot be cast to arv
at arv.j(SourceFile:178)
at arv.h(SourceFile:205)
at abv.h(SourceFile:1267)
at ats.k(SourceFile:1380)
at ats.S(SourceFile:663)
at ats.d(SourceFile:619)
at net.minecraft.client.main.Main.main(SourceFile:101)