Problem in android java plugin

Hello, i am new in android unity. I follow the tutorial Java plugin tutorial and did as it. When i clicked on ""call java " button ,i get error in initialising android javaObject. Error i get-

07-29 18:14:07.372: E/dalvikvm(6512): JNI ERROR (app bug): accessed stale global reference 0x1d20027e (index 159 in a table of size 159) 07-29 18:14:07.372: E/dalvikvm(6512): VM aborting 07-29 18:14:07.382: A/libc(6512): Fatal signal 11 (SIGSEGV) at 0xdeadd00d (code=1), thread 6531 (UnityMain)

Please help me to come out from this problem. Thanks in advance.