The fix is proper grounding : connect the mains ground to the computer case.
I was facing the same problem last year - the ethernet was working only
after 5 or 6 periodical reboots. I read also about those grounding
tricks at VIA Arena forums, but the reason is that Morex was simply a
little underpowered. My EPIA combination draws power at start a bit more
than the Morex can offer and my fix was to put a big capasitor next to
Morex DC-to-DC card to smooth the power draw at start. IMHO a cleaner
solution than mess up with the grounding...