You may be referring to this issue
https://jira.jboss.org/browse/JBIDE-501
For the plugin to know that jboss is started; it will try to locate default urls using default settings. This changes from version to version.
One solution would be to change the server name and port:
80 -> 8080 or vice versa
localhost -> 127.0.0.0.1 or vice versa
http://community.jboss.org/servlet/JiveServlet/downloadImage/5434/393-146/jboss+settings.bmp
See if this helps