JBoss deployment Problem

I m tring to deploy a exploded archive on Jboss4.
For the first time it deploys it fine.
But whenever i change any piece of code and try to redeploy it,it gives me a blank error box.After closing the box,it gives the following warning in the deployment window...
"Deployment is out of date due to changes in the underlying project contents.you'll need to manually redeploy the project to update the deployed archive."

Other than this it sometimes also deletes the .war files it creates for the application.

Any leads why this happens???