2012-02-22 15:39:51 [SEVERE] java.lang.IllegalArgumentException: Don't know how to add class net.minecraft.server.EntityMinecart!
2012-02-22 15:39:51 [SEVERE]    at net.minecraft.server.EntityTrackerEntry.b(EntityTrackerEntry.java:429)
2012-02-22 15:39:51 [SEVERE]    at net.minecraft.server.EntityTrackerEntry.b(EntityTrackerEntry.java:222)
2012-02-22 15:39:51 [SEVERE]    at net.minecraft.server.EntityTracker.updatePlayers(EntityTracker.java:150)
2012-02-22 15:39:51 [SEVERE]    at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:548)
2012-02-22 15:39:51 [SEVERE]    at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:441)
2012-02-22 15:39:51 [SEVERE]    at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)
2012-02-22 15:39:51 [SEVERE] Unexpected exception
java.lang.IllegalArgumentException: Don't know how to add class net.minecraft.server.EntityMinecart!
        at net.minecraft.server.EntityTrackerEntry.b(EntityTrackerEntry.java:429)
        at net.minecraft.server.EntityTrackerEntry.b(EntityTrackerEntry.java:222)
        at net.minecraft.server.EntityTracker.updatePlayers(EntityTracker.java:150)
        at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:548)
        at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:441)
        at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)