When I join my server it stops an give an error in the console! I'm using an clear an untouched minecraft version!

04.08 12:51:40 [Server] Server thread/INFO Saving players
04.08 12:51:40 [Server] Server thread/INFO Stopping server
04.08 12:51:40 [Server] INFO at java.lang.Thread.run(Unknown Source) [?:1.7.0_55]
04.08 12:51:40 [Server] INFO at net.minecraft.server.MinecraftServer.run(SourceFile:445) [Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at net.minecraft.server.MinecraftServer.x(SourceFile:529) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at ph.y(SourceFile:303) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at net.minecraft.server.MinecraftServer.y(SourceFile:623) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at qu.c(SourceFile:147) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at gp.a(SourceFile:187) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at ri.c(SourceFile:54) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at ri.b(SourceFile:96) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at sf.a(SourceFile:131) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at sf.c(SourceFile:276) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at sf.a(SourceFile:224) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at qi.a(SourceFile:263) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at qi.a(SourceFile:231) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at qj.<init>(SourceFile:39) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at qk.c(SourceFile:85) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at qk.e(SourceFile:133) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at bet.a(SourceFile:83) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at bet.a(SourceFile:95) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at bet.a(SourceFile:330) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at wq.a(SourceFile:162) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO at wk.f(SourceFile:1195) ~[Latest_Snapshot.jar:?]
04.08 12:51:40 [Server] INFO java.lang.NoClassDefFoundError: Could not initialize class b
04.08 12:51:40 [Server] Server thread/ERROR Encountered an unexpected exception