SomeOne posted the solution below however it does not work becuase when I do that I get another error.
Please advise.
In your "arcadeos.cfg", find that line :
arcmodeopt=-monitor arcade
simply remove "-monitor arcade" (so you just let "arcmodeopt=")
It will correct your problem.
I think that this is a command that isn't understood anymore by advancemame
> AdvMAME & ArcadeOS: unknow command line option "-monitor"
> This is the message I get...
> Would someone please have an idea on what I have to do now ?