I recently upgraded my iPhone 4 to custom FW 4.2.1. One strange problem I notice is that when I switch to video mode and start recording, the screen turns slightly dark after 38 seconds as if it will automatically lock the phone. The video ends from there. So meaning I can only record up to 38 seconds. I already restored my phone back to the custom FW 4.2.1 but still having the same issue. Is there a bug somewhere that its causing this?