MyTabList error

10:39:44 [SEVERE] Exception in thread "pool-1-thread-737"
10:39:44 [SEVERE] org.apache.commons.lang.UnhandledException: Plugin MyTabList v1.4 generated an exception while executing task 21
	at org.bukkit.craftbukkit.v1_6_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NoClassDefFoundError: org/mcsg/double0negative/tabapi/TabAPI
	at me.Gamecraft3D.MyTablist.start$1.run(start.java:88)
	at org.bukkit.craftbukkit.v1_6_R3.scheduler.CraftTask.run(CraftTask.java:53)
	at org.bukkit.craftbukkit.v1_6_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
	... 3 more