Britney Spears - who as of late has been spied looking leaner and meaner (and with her nether regions covered up) - apparently had been quietly preparing to put on a surprise performance at the Los Angeles nightclub Forty Deuce, but wound up cancelling at the last minute. Sources tell that while Spears was itching to test the waters with a small-scale showcase, it was ultimately decided that the recent rehabber wasn't quite ready. The latest buzz is that she might instead turn up at a Southern California House of Blues sometime this week - or, if all else fails, at your neighborhood Japanese karaoke bar.