My phone doesn't allow me to answer incoming calls

[AC Question]

If I receive a call it rings but I keep getting a pop-up saying something like: "Phone stopped". Maybe I "forced stopped" it unintentionally. But it keeps popping up even if my phone stops ringing. And keep pressing "ok". The only time it stops popping up is when I restart my phone. Pleassssee help!! I need to answer calls. Thnx xxx