Ravi,
Sorry that you are seeing this issue.
1. Can you please check if the issue only exists with JBoss server and whether the ‘Add Deployment’ works fine for all other servers?
2. Can you check if you can add deployment for a simple Web project to JBoss from context menu Run As > MyEclipse Server Application > JBoss ?
3. Can you please switch to a new workspace and check if the issue exists ? If you are not seeing the issue on a new workspace, then please import your projects to the new workspace.If you are looking at preserving the settings , copy the .metadata/.plugins/org.eclipse.core.runtime/.settings directory into your new workspace directory.
4. In case the issue exists in new workspace too, then please share the Installation Details from MyEclipse > Installation Summary > Installation Details. Please list the third party plugins which you have installed.
5. Also check for any errors of interest in the .log file which is located at <workspace dir>/.metadata/.log and paste them here for us to take a look.