Help Problems with stock navigation app

[rubing]

I am using the navigation app while plugged in to the car dock and am having the problem of the screen going black. The phone screen does not turn off rather it remains on but the navigation app is all blacked out, so I'll need to press the home button to get out of it and then restart the phone. This happens when I am using the navigation app and then interrupted by another app. For example, I am driving along with navigator on and then receive a phone call. I switch to the phone and then when I switch back to navigation is completely black. Any advice on how I can try to fix this? Thanks!!!