I have/had a simular problem with a Digiboard driver on SCO locking up with no logged info until you rebooted. Then it said failure at port (x). So I reseated the memory as it is stored on the same address block for some reason (COMPAQ!!
), and this stopped it for almost a month. Then 3 days ago it started back but it was at 10:30 Monday morning, then 9:30 Tuesday, and 8:30 yesterday. (Those times are rounded off ball park figures by the way).
Anyhow, I replaced the Multi-serial interface card today. We'll see if that does the trick.
Hope some of this helped in your search for the cure.