UPDATE:

honda customer relations opened a "case" and referred it to the regional customer service representative. she looked up the info on the 90/91 accord warranties for the supplemental restraint systems and decided that no matter what the root cause was, honda would cover all costs to determine what was wrong w/ the seatbelt mechanism and replace whatever was needed to get them to function properly again.

i dropped off the accord yesterday evening. i just got a call a few minutes ago and they figured out what it was and ordered the part overnight, so it should be back together in one piece tomorrow afternoon.

it's nice to know that they'll still cover stuff like this w/ a 16-yr-old car that has 263+ thousand miles. i guess it may have also helped that i was curteous at all times with the customer relations people and that this is my 4th accord and my 7th honda/acura vehicle overall.