Do you have a 0.1uF across +5 and GND as close to the processor's power pins as possible?
Do you have any fast-switching digital pins close to AVCC, AREF, or the Analog Input pins?
Did you try a capacitor on AREF?
Have you checked Grumpy_Mike's website for de-coupling advice?
AREF is not connected on the diy bb arduino (see previous response)
Yeah I do have some sort of idea of the importance of decoupling, I am more interested in why not having aref connected is causing problems.. from what i read the adc defaults to vcc for its reference voltage, and since the pots are also hooked up to the same vcc, they should track with ahy ripple.... shouldn't they?
Still a little confused, but I am getting there... So even if I need the internal reference of vcc, I should still have a cap from aref to gnd.. Is there a reason why it works fine off the duemilenove? Is it just that it provides a little more than 5v therefore any ripple would still keep it above 5v?