Is StockQuotePortImpl your class? Is it a servlet? Looks like you have an invalid cast and need to fix your code. The part of the stack trace that you did not post should tell you while line has the problem (assuming you compiled with debug options).
By the way, if the class is a servlet then the issue has nothing to do with web services, and thus this post is in the wrong forum (the beginner's forum would have been better).