[16:50:03 FATAL]: Fatal error launching game. Report this to http://bugs.mojang.com please!
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901) ~[?:1.8.0_25]
at java.util.ArrayList$Itr.next(ArrayList.java:851) ~[?:1.8.0_25]
at net.minecraft.launcher.updater.MinecraftVersionManager.getInstalledVersions(MinecraftVersionManager.java:185) ~[launcher.jar:1.6.11]
at net.minecraft.launcher.Launcher.cleanupOrphanedVersions(Launcher.java:430) ~[launcher.jar:1.6.11]
at net.minecraft.launcher.Launcher.performCleanups(Launcher.java:494) ~[launcher.jar:1.6.11]
at net.minecraft.launcher.game.MinecraftGameRunner.launchGame(MinecraftGameRunner.java:221) ~[launcher.jar:1.6.11]
at com.mojang.launcher.game.runner.AbstractGameRunner.onDownloadJobFinished(AbstractGameRunner.java:186) [launcher.jar:1.6.11]
at com.mojang.launcher.updater.download.DownloadJob.popAndDownload(DownloadJob.java:122) [launcher.jar:1.6.11]
at com.mojang.launcher.updater.download.DownloadJob.access$000(DownloadJob.java:12) [launcher.jar:1.6.11]
at com.mojang.launcher.updater.download.DownloadJob$1.run(DownloadJob.java:86) [launcher.jar:1.6.11]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [?:1.8.0_25]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_25]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [?:1.8.0_25]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [?:1.8.0_25]
at java.lang.Thread.run(Thread.java:745) [?:1.8.0_25]

^ Above is the issue. I have no clue what it means, but it is making my server connections very slow.