I was about to report a bug that when you are on homescreen, when you press the DIAL "green" button, It wouldn't open. At first, I thought something was wrong with the my key because I had dropped my phone early morning.
Then received NRG's Tweet.
So just press the Start menu > then GREEN Key to enter Dial mode.
NRGZ28
Well Cookie himself says the phone key bug is a confirmed issue. Workaround until then... just open the start menu, then you can open dialer