:-) The neon is sending a noise trough de lines... how do you start the neon? do you get some of the ports outputs, connects to a driver transistor that switch the relay's contacts?

You can try filter capacitors... I would prefer a opto-switch... your port lits a LED, that is pointed to a foto-transistor (not conected to your MCU board in ANY way!) in that board, when lit, your photo-transistor will drive another transistor and switch the relay... and things should be okay...

HTH

orlando