Found the problem: when I use " ADCIN 1, Press " instead of

Press.highbyte=ADRESH 'move result of highbyte to Press
Press.lowbyte=ADRESL 'move result of lowbyte to Press

the ADC works correctly. I have used this code many times with other pic's and it always worked. Have to find out why it gave me a headache with this chip.
Thanks everyone for the help, it was a pleasure.