Hello,
I have bought a HTC 8X phone last week, and I experience the same problem. When I want to unlock the screen after a long time (a few hours), it's frozen with written "Resuming...". I have to start it again by pressing the start button. After a few reasearch on internet, it seems that a lot of people experience this problem with HTC phones and also Nokia lumia phones. Does it come from windows phones ? I've desactivated any background activity and as it new, I have only a few application installed like whatsapp, skype and facebook, so I don't see where it comes from. Has anyone find a solution ?