Cakewalk UA-4FX Guitar Sound Problem!!!

Hi,

I have the following problem with the UA-4FX.

When I plug the guitar into UA-4FX with the switch to Guitar and hear the Signal in Guitar Rig and Amplitube or sonar If there is cracking in the signal.

Where is the UA-4FX to mic. crack and then is gone but the sound has more drive.
My Settings on UA-4FX (Advanced mode / ON - Sample rate 44.1 - Source Analog)

Is the UA-4FX broken or is it a genaral problem?