Some of the things you could try:
1) Let JBoss start successfully. Then start your debug mode in Eclipse (for this to happen, you should configure suspend=n in the JAVA_OPTS in run.bat for JBoss).
2) In the "Breakpoints" window of your project, if you see any breakpoints already set, then remove them.
3) In the "Debug..." window of Eclipse, remove/delete any existing debug configurations. Then create a new configuration.