Half of the HTC EVO 4G screen is unresponsive I have a HTC EVO 4G, which I got around 6 months ago.

Just recently, the lower half of my phone's screen has become almost completely unresponsive. 

For instance, I wanted to allow the use of non-market apps. The confirmation screen that tells me that this could potentially be dangerous is not selectable because of the screen being non-responsive. 

How can I fix this? Do I send it back to be repaired?
Your digitizer probably failed.  That is the glass piece you touch with your finger.  On some models it can be replaced, although not something for the faint of heart.  I have had to do this for my EVO 3D.