Have been having this problem for the Moment for a while now. Once a call is placed the phone will go black and I am unable to access the onscreen functions (Speaker, Dialpad, etc). I've tried tapping the screen, hitting the back button and hitting the menu button, but the screen remains black. At some point it MAY come on or just briefly flash on. This has been very annoying - especially with calls that require multiple prompts. Any advice on help?