This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
This type of error is thrown when a application tries to call a abstract method. Once I got this type of error when i changed the signature of bean and redeployed it the app server. It got solved after undeploying the existing bean & deploying the new version instead of redeploying directly.
I've only ever encountered it once when I had changed an abstract class but forgotten to deploy the changed version of a derived class to the web application. The derived class misses a method that is called so the call is relegated to the mother class in which it is abstract and thus can never be called.