Just tried your suggestion and moved EVERYTHING, and I do mean everything, to an "old" folder that isn't set to sync. Checking the Gmail app, it's only set to sync my Inbox, and nothing else. Even with an empty inbox and no other folder set to sync, it still force closes. If I disable that account and enable my secondary, sure enough the force closes stop.
This is really bizarre. I'm relatively new to the Android modding/hacking thing, so could you point me to this FXZ thing you're talking about? I figure I might as well give it a try if it's feasible.