abhijeetmohite,
Can you answer some more questions for me to understand the issue better ?
1) Share your build id from Help > About MyEclipse Enterprise Workbench > Build Id. Paste it here.
2) Are you trying to migrate the project ? If yes then from which app server are you trying to migrate it ?
3) Which database are you trying to communicate with ?
4) Clear the contents of the .log file which is located at <workspace dir>/.metadata/.log. Now replicate the issue and paste the entire error message here.
5) Here are a couple of threads which discuss the same issue. Please have a look and give the solutions discussed a try.
http://community.jboss.org/message/250797
http://www.coderanch.com/t/444551/JBoss/ClassCastException-JBOSS-GA
http://www.coderanch.com/t/443132/JBoss/ClassCastException-Jboss
http://www.coderanch.com/t/463211/JBoss/getting-org-jboss-resource-adapter
Let me know how this works for you.