2012-06-26 22:44:36 [INFO] [CasinoSlots] Enabling CasinoSlots v2.3.1
2012-06-26 22:44:36 [SEVERE] Error occurred while enabling CasinoSlots v2.3.1 (Is it up to date?)
java.lang.NullPointerException
at org.bukkit.Location.getBlock(Location.java:82)
at com.craftyn.casinoslots.slot.SlotData.getBlocks(SlotData.java:147)
at com.craftyn.casinoslots.slot.SlotData.loadSlot(SlotData.java:130)
at com.craftyn.casinoslots.slot.SlotData.loadSlots(SlotData.java:80)
at com.craftyn.casinoslots.util.ConfigData.load(ConfigData.java:53)
at com.craftyn.casinoslots.CasinoSlots.onEnable(CasinoSlots.java:75)
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:215)
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:337)
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:381)
at org.bukkit.craftbukkit.CraftServer.loadPlugin(CraftServer.java:256)
at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:238)
at net.minecraft.server.MinecraftServer.t(MinecraftServer.java:381)
at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:368)
at net.minecraft.server.MinecraftServer.init(MinecraftServer.java:197)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:432)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)

No idea why it started again. It started about a week ago and I was hoping it would clear up again automatically. No such luck.

Okay well I've found the root of this, but sadly there's nothing that I can do about this since it varies in all different aspects. But I've made a change to CasinoSlots in the near future that will tell you which slot is causing this error that way you can go in the slots.yml and remove it and recreate it. See this commit: e6cfabd

Have you changed worlds where one of your slot machines was? Because if so, then that is why.