помогло, но мне вот это не нравится:

update not found: old 591dacd1bdd07d064c99013304aba73a, new: 591dacd1bdd07d064c99013304aba73a
java.lang.NullPointerException
at java.io.Reader.<init>(Unknown Source)
at java.io.InputStreamReader.<init>(Unknown Source)
at net.minecraft.src.AchievementMap.<init>(AchievementMap.java:19)
at net.minecraft.src.AchievementMap.<clinit>(AchievementMap.java:40)
at net.minecraft.src.StatBase.func_25068_c(StatBase.java:41)
at net.minecraft.src.StatBasic.func_25068_c(StatBasic.java:23)
at net.minecraft.src.StatList.<clinit>(StatList.java:178)
at net.minecraft.src.Item.<clinit>(Item.java:376)
at net.minecraft.src.Block.<clinit>(Block.java:885)
at net.minecraft.src.TextureWaterFX.<init>(TextureWaterFX.java:20)
at net.minecraft.client.Minecraft.<init>(Minecraft.java:44)
at net.minecraft.src.MinecraftAppletImpl.<init>(MinecraftAppletImpl.java:15)
at net.minecraft.client.MinecraftApplet.init(MinecraftApplet.java:33)
at net.minecraft.Launcher.replace(Launcher.java:166)
at net.minecraft.Launcher$1.run(Launcher.java:108)

перед этим, как я понял, клиент не смог загрузить какойто апдейт - вроде с ачивками