Hey Adam, thanks for your help. I appreciated too much. Listen, you wrote this:

"I would double check all the intended ground connections to see if some might be forgotten.

Maybe some of the unused / un-terminated pins are picking up noise."

Are you suggesting that I should connect all the unused pins to ground?? And what is exactly all the intended ground connections? I mean, I only have de gnd pin connected to ground, well and the capacitor too. I also have the 10 microfarad capacitor in parallel with the 100 nanofarad capacitor...

Thanks for your help!

Armando.