IOS 4.3 hide status bar permanently

Try this:

[[UIApplication sharedApplication] setStatusBarHidden:NO withAnimation:UIStatusBarAnimationFade];

From Apple Class Reference:

setStatusBarHidden:withAnimation:

Hides or shows the status bar,
optionally animating the transition.
– (void)setStatusBarHidden:(BOOL)hidden
withAnimation:(UIStatusBarAnimation)animation
Parameters

hidden
YES to hide the status bar, NO to show the status bar.

animation
A constant that indicates whether there should be an animation and, if
one is requested, whether it should
fade the status bar in or out or
whether it should slide the status bar
in or out.