Newly introduced bug!!!
Problem occurs immediately following my checking the "submit config file" option in the sociable classic options area. All pages across the site stop loading all content after the page header. Admin area appears unaffected, except for the options page for the regular sociable plugin. This means that I can't get in to turn off that option. (I found the option in serialized option data with PHPmyadmin, but that's not for the faint of heart).
Problem has occurred on multisite (haven't tested standalone) install in two different sites, one running twentyeleven, and the other twentyten, with all plugins disabled. (Always the first thing I check.)