Why is my galah vicious now but never use to be?

[ChickenLittle]

I have a pet Galah, I got him when he was about 4 months old and have had him over a year now. He was tame when I bought him and loved to be held and payed lots of attention. Now all a sudden he doesnt like me going near him, he bites me really hard and wont let me pick him up or anything. Its really frustrating because it just happened out of the blue a few weeks ago and now its getting worse. Like he lives in his cage in our lounge room so he gets plenty of attention from us, but just yesterday I let him out of his cage and when he flew to the floor I called him over so I could pick him up and put him back on the cage and he charged at me with his beak ready to rip a hole in me, it was like a death strike. I really dont know what is wrong with him and why he's acting like this. Has anyone got any ideas? I am at my wits end with him.