Some updates:

Tom: I've switched and swapped every board that plugs into the motherboard with known working ones. It has no effect. I've looked, and it seems that the  cards make good contact, but i'll keep testing. Right now, I'm looking into broken circuits on the board, but I'm running out of things to test...

snhirsch: I've already cleaned the board with full immersion in 50% water and vinegar. It did brighten things up a bit, but unfortunately, had no effect on the functionality of the board. The gold fingers on the card look brand new: no scratches, marks, corrosion, etc, so I doubt that's the problem. 

--
--
-----
You received this message because you are a member of the LisaList group.
The group FAQ is at http://lowendmac.com/lists/lisa.html
To post to this group, send email to lisalist@googlegroups.com
To leave this group, send email to lisalist+unsubscribe@googlegroups.com
For more options, visit this group at http://groups.google.com/group/lisalist
---
You received this message because you are subscribed to the Google Groups "LisaList" group.
To unsubscribe from this group and stop receiving emails from it, send an email to lisalist+unsubscribe@googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.