Here is the latest. I made the changes you suggested, unfortunately without success. Here is what the image section of my lilo.conf file looks like for the relevant boot area:
append="devfs=mount quiet acpi=off"
Basically things are the same. Please let me know if my syntax is wrong. Incidentally I did run /sbin/lilo and then rebooted. I tried it with both acpi=off and pci=noacpi.
I'm very sorry to bother you with this, but I feel like we're close here. Any other thoughts?