What causes this error and how do i fix?

Whenever players join my server it gives me this: [SEVERE] at sun.net.www.http.HttpClient.<init>(Unknown Source)
2012-02-04 20:48:33 [SEVERE] at sun.net.www.http.HttpClient.New(Unknown Source)
2012-02-04 20:48:33 [SEVERE] at sun.net.www.http.HttpClient.New(Unknown Source)
2012-02-04 20:48:33 [SEVERE] at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
2012-02-04 20:48:33 [SEVERE] at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
2012-02-04 20:48:33 [SEVERE] at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
2012-02-04 20:48:33 [SEVERE] at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
2012-02-04 20:48:33 [SEVERE] at java.net.URL.openStream(Unknown Source)
2012-02-04 20:48:33 [SEVERE] at me.ahniolator.plugins.sunburn.Sunburn.getCurrentVersion(Sunburn.java:609)
2012-02-04 20:48:33 [SEVERE] at me.ahniolator.plugins.sunburn.Sunburn.checkForUpdates(Sunburn.java:589)
2012-02-04 20:48:33 [SEVERE] at me.ahniolator.plugins.sunburn.BurningPlayerListener.onPlayerJoin(BurningPlayerListener.java:25)
2012-02-04 20:48:33 [SEVERE] at org.bukkit.plugin.java.JavaPluginLoader$1.execute(JavaPluginLoader.java:270)
2012-02-04 20:48:33 [SEVERE] at org.bukkit.plugin.RegisteredListener.callEvent(RegisteredListener.java:57)
2012-02-04 20:48:33 [SEVERE] at org.bukkit.plugin.SimplePluginManager.callEvent(SimplePluginManager.java:453)
2012-02-04 20:48:33 [SEVERE] at net.minecraft.server.ServerConfigurationManager.c(ServerConfigurationManager.java:129)
2012-02-04 20:48:33 [SEVERE] at net.minecraft.server.NetLoginHandler.b(NetLoginHandler.java:121)
2012-02-04 20:48:33 [SEVERE] at net.minecraft.server.NetLoginHandler.a(NetLoginHandler.java:40)
2012-02-04 20:48:33 [SEVERE] at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:61)
2012-02-04 20:48:33 [SEVERE] at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:536)
2012-02-04 20:48:33 [SEVERE] at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:434)
2012-02-04 20:48:33 [SEVERE] at net.minecraft.server.ThreadServerApplication.run(SourceFile:465)

And disconnects them. Please help!

Wait...ok ima try deleting this outdated plugin i have.... -_- that will prob fixit. sorry im stupid.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.