iOS the screen gets dimmed when called from NSNotification

[bluehill]

when i call a alertview from NSNotification function the alertview is called but the screen gets dim.
This function is already getting called from a thread(NSInvocationOperation).

like the screen in following url...
http://stackoverflow.com/questions/4325403/nsnotification-stops-method-from-working-completely

i tried to use the solution provided in the same url but couldn't succeed...
The solution is as follows

When you call the method from the NSNotificationCenter, the method is not on the GUI thread. You have to execute the AlertDialog show and TableView reloading on the GUI thread using performSelectorOnMainThread

-(void)reloadMainView:(NSNotification*)notify{
	self.navigationItem.rightBarButtonItem = nil; 
	[self.view setNeedsDisplay];
	
	/*
         [self.view performSelectorOnMainThread:@selector(updateComplete) withObject:nil waitUntilDone:[NSThread isMainThread]]; */

}

-(void)updateComplete{
	NSLog(@"timere claled");
	UIAlertView *alert = [[UIAlertView alloc] 
						  initWithTitle: @"Update complete" 
						  message:@"Update will take effect on next startup."
						  delegate:self
						  cancelButtonTitle:@"OK"
						  otherButtonTitles:nil];
	
	[alert show];
	[alert release];
}