GhostofCain
Ancient Mariner
It might be multiple things. Bruce's book coming out and him feeling like he's being diminished in it, IESF still bothering him, this whole "I was meant to be a star producer" thing popping up again as a result, etc. It feels like he expected the Maiden reunion to play out one way (Bruce and Adrian rejoin, he gets the producer gig, everyone is happy I guess) and when it didn't work out, he grew bitter about it, and it's finally bubbling to the surface.
Bruce speaks quite highly of Roy Z in the book, so I do not know what he was expecting...