I too encountered this error a while back. I believe the solution was to upgrade to JDK 1.3.1. If you do try this for lack of a better option, I suggest 1.3.1_04 because I've read about and experienced some funky incompatibility with 1.3.1_02 or less. (The funk was that the ClassLoader was not recognizing/finding a ton of classes leading to a stream of ClassDefNotFound errors.) I have no experience with 1.4.0 so I can't speak for that though I expect it would work too.
Good luck and please let us know if that clears it up so others will know whether or not to do the same.
right. the problem went away after i switched to jdk1.3.1_04. Thanks.