This could go two ways. Yes I'd say it's a bit of a bug that the picker doesn't resize accordingly, but it could also be argued that Apple expects the picker to operate in a non-full screen environment.
Rather than try to force it to work as you'd like, I'd instead recommend turning the status bar back on while the picker is visible:
[[UIApplication sharedApplication] setStatusBarHidden:NO animated:YES];
(To confirm, you are turing the status bar off in a similar fashion with your app, not just somehow painting over it?)
Mike Abdullah
2009-09-10 11:04:24