General :: Sony Xperia Neo L / Paranoid CM9 - No Screen To Answer The Call

I am using Sony Xperia Neo L with ported Paranoid CM9 rom with CM9 OC Gov Net kernel. I have used it for a few months until today, I can't receive phone calls but can still make phone calls. When somebody calls me, the phone will just vibrate for less than a second. I can see who is calling me in the call logs. There isn't a screen for me to answer the call: with a call icon which can be pulled left or right. The caller would just hear my neo L's voicemail greeting or like forwarding to another phone ( i know that because the beeping sound is different.) I have checked the forwarding setting already.