Loud guitar buzz feed. Help me kill it! Cubase ai5 ci2

I have a major problem with loud guitar buzz feedback. I use ci2 with cubase ai5! The buzz noise appears when i start a new project. I have plugged my guitar into the ci2 and when i enable the guitar track the noise is loud and i cant kill it. I have tried changing the buffersize in setup. I have tried disableing the mic in the computer. Still the buzz feed just roars out loud. Please help me!