The first rumble of trouble concerning Sabine [1915 Westheimer, (713)529-7190] reached my ears last month, when I heard that the neo-Southern restaurant’s general manager, Keith Thompson, had jumped ship to owner/chef Frederic Perrier’s self-named cafe [Café Perrier, 4304 Westheimer, (713)355-4455]. Not such a big deal, in and of itself; such…