Sorry, I should have been a bit less vague in my last email. Usually
Arch's wiki is pretty good at handling these scenarios, but unfortunately it's not helpful in this regard.
GNOME 3's Mutter and xmonad don't play nice together, so in the past xmonad users have always used GNOME's fallback mode (i.e. Metacity). There was some brouhaha when GNOME announced they were going to
drop fallback mode due to lack of support, but after a lot of complaints they
reversed that decision.
In either case, I've always used xmonad in conjunction with GNOME 3.x in the past but the latest upgrade to 3.8 has broken the configuration. Entering the desktop leaves a broken state where the thing visible is a grey background and a black bar where the top panel should be.
I'm guessing that something changed in the back end and that's what broke
xmonad, however I'm not sure where to start debugging the issue.
Thanks for reading,
William