Error

2013-04-12 21:01:36 [SEVERE] Could not load 'plugins/BKCommonLib.jar' in folder 'plugins'
org.bukkit.plugin.InvalidDescriptionException: Invalid plugin.yml
	at org.bukkit.plugin.java.JavaPluginLoader.getPluginDescription(JavaPluginLoader.java:257)
	at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:132)
	at org.bukkit.craftbukkit.v1_5_R2.CraftServer.loadPlugins(CraftServer.java:239)
	at org.bukkit.craftbukkit.v1_5_R2.CraftServer.<init>(CraftServer.java:217)
	at net.minecraft.server.v1_5_R2.PlayerList.<init>(PlayerList.java:55)
	at net.minecraft.server.v1_5_R2.DedicatedPlayerList.<init>(SourceFile:11)
	at net.minecraft.server.v1_5_R2.DedicatedServer.init(DedicatedServer.java:105)
	at net.minecraft.server.v1_5_R2.MinecraftServer.run(MinecraftServer.java:379)
	at net.minecraft.server.v1_5_R2.ThreadServerApplication.run(SourceFile:573)
Caused by: org.yaml.snakeyaml.error.YAMLException: java.util.zip.ZipException: invalid LOC header (bad signature)
	at org.yaml.snakeyaml.reader.StreamReader.update(StreamReader.java:199)
	at org.yaml.snakeyaml.reader.StreamReader.<init>(StreamReader.java:63)
	at org.yaml.snakeyaml.Yaml.load(Yaml.java:411)
	at org.bukkit.plugin.PluginDescriptionFile.<init>(PluginDescriptionFile.java:42)
	at org.bukkit.plugin.java.JavaPluginLoader.getPluginDescription(JavaPluginLoader.java:252)
	... 8 more
Caused by: java.util.zip.ZipException: invalid LOC header (bad signature)
	at java.util.zip.ZipFile.read(Native Method)
	at java.util.zip.ZipFile.access$1400(Unknown Source)
	at java.util.zip.ZipFile$ZipFileInputStream.read(Unknown Source)
	at java.util.zip.ZipFile$ZipFileInflaterInputStream.fill(Unknown Source)
	at java.util.zip.InflaterInputStream.read(Unknown Source)
	at java.io.FilterInputStream.read(Unknown Source)
	at java.io.PushbackInputStream.read(Unknown Source)
	at org.yaml.snakeyaml.reader.UnicodeReader.init(UnicodeReader.java:84)
	at org.yaml.snakeyaml.reader.UnicodeReader.read(UnicodeReader.java:114)
	at java.io.Reader.read(Unknown Source)
	at org.yaml.snakeyaml.reader.StreamReader.update(StreamReader.java:183)
	... 12 more