This machine is a 2004 model used for tig with a water cooled torch
and foot pedal remote control. (...)

Have you tried "Reset to Factory Settings" yet?
From: http://www.millerwelds.com/om/o363w_mil.pdf

"To reset all welding power source functions
to original factory settings, turn power off.
Push and hold the Process, Amperage,
Output, and Start controls and turn On power.
Hold switch pads for approximately 7
seconds (or until software version number
_ _ _ _ _ _-_clears meters)."

--Winston