How very strange...
No, I'm sorry, I do not have any other solutions. Although, the Brawl disc (and some others) are dual-layered; when I had this problem, my older non-Brawl games worked just fine as well because they were not dual-layered.
http://www.nintendo.com/consumer/repair/dld_repair_home.jsp?problem=DLDNODISC&gameCode=SSBB explains what happened to me.
Still, if Brawl is working without the hacks, then I do not have a clue as to what it could be.
Sorry I could not help.