We've been juggling half a dozen projects, and haven't had the time to get back to this. I believe we found the problem. Pin 14 of one the chips snapped off while attaching the line to it (apparently very easy to do due to all the bending involved). We dug away some of the package material to expose some of the lead inside, but I don't think it was quite making contact with the lead. We'll dig a little more and pray we don't run into the die.

Stu