It seems intelliscreen can lockup if you get a push calendar notification as from exchange if you have unread email. The problem is when you get an alert, intelliscreen will ‘flip up’ so show the alert and a button to dismiss it. However, if you have unread email, you cannot access the slide bar to turn on the phone. Turn the phone off and it will repeat the process because accepting the alert does not get sent.
So what is the fix? Well, you will not like this, but you only have 2 options. Go onto another computer and read all your email. Or, reboot the iphone and access the phone before intelliscreen starts up.
Now if you are connected to a wifi, you can sometimes read the email from intelliscreen and it ‘MAY’ send the ‘read’ command back to your email service and thus get out of the loop.
I’ve only seen this happen a few times, so as I keep trying other fixes, I’ll update this post.