minecraft server error
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this happened a while ago and i re downloaded the server thing from minecraft.net and it still wont work! when i start it this comes up:
[INFO] Starting minecraft server version Beta 1.7.2
[INFO] Loading properties
[INFO] Starting Minecraft server on *:25565
[INFO] Preparing level "world"
[SEVERE] Unexpected exception
java.lang.NullPointerException
at dp.c(SourceFile:81)
at dj.a(SourceFile:1892)
at hi.d(SourceFile:469)
at he.c(SourceFile:75)
at he.b(SourceFile:96)
at dj.c(SourceFile:313)
at dj.a(SourceFile:270)
at dj.f(SourceFile:274)
at dj.a(SourceFile:211)
at os.a(SourceFile:51)
at dj.c(SourceFile:186)
at dj.<init>(SourceFile:163)
at dp.<init>(SourceFile:34)
at net.minecraft.server.MinecraftServer.a(SourceFile:201)
at net.minecraft.server.MinecraftServer.c(SourceFile:162)
at net.minecraft.server.MinecraftServer.run(SourceFile:284)
at bq.run(SourceFile:422)
anyone know what this means or how to fix it!?