hi zhi,
i had also faced the same problem , long back ago ,
the problem exactly in my case was that one of my function was not according to specification(ejbPostCreate), well in ur case , u have to look to the log file and there it is clearly mentioned where exactly the error encountered , c this error comes many times , rather i should say it's a common error , so better check out at what time this error is being fried by the server,
when server deploys an application or a bean .
first it complies it then it make it's stub and tie and the bounds them , so check it out at what time it giving the error.
hope this will help u
feel free to mail me on dsumani@yahoo.com
cheers
deepak