Very strange: PIC24F32KA301 CTMU reading changes with ICD3 being connected/disconnected (Szidor)

Hi! I am using the following code to detect a touch sensor on a PIC24F32KA301: AD1CON1bits.ADON = 1; CTMUCON1bits.CTMUEN = 1;... AD1CHS = an; CTMUCON1bits.IDISSEN = 1; US; US; US; US; US; US; US; US; US; US; // I tried many delays from 1us to 100us CTMUCO..