You might have a look into the logfiles and find out whether you have exact one point where the time was spend.
Maybe you can set TRACE for the root logger.
You can compare the startup between both instances.
Does this happen also if you use two fresh unzipped instances?
So you mean it could be related to the server config itself and has nothing to do with JBoss?
I'll try it with 2 fresh instances as you suggested and will come back to you.