I'm posting this issue regarding the same problem I have on my iPhone 4. This issue is similar to a past post linked here: http://forums.macrumors.com/showthread.php?t=1021256. I'm having exactly same problem with the post in the link. Does anyone know any fix for it? Or what has caused to the problem? The slider enlarges and we can't slide to power off or unlock the screen. Is it caused by any Cydia apps? My phone is running on iOS 4.2.1, jailbroken. Thanks. Replies are welcomed.