From the datasheet, I am using:

ADCON1 = %00001101

which specifyes that I am using the project's voltage internally from VDD and VSS for voltage reference. I also tried using external voltage for reference but I get the exact same results.

I tried putting a .1uF cap at the voltage in pin but no change.

I am going to tried with another sorce of 5v and not use the USB to see what happens.

Any suggestions will be appreciated.

Javier.