Sorry to keep you guessing on the OS -- Slackware 8.1 on an aging IBM Aptiva.
Yes, the system has worked in the past, very recently in fact. I wish I could tell you that I changed a config file or a set of permissions, anything. But I can't think of a single change. So it has to be something unremarkable.
I set "export LD_DEBUG=libs" in nsd-postgres and exported an output file. The other options (detail and basic) returned errors in Slackware so I dropped them. But the libs option was good. I searched the debug output file for occurances of libpq.so.2. It never turned up. So I searched for "libpq" and "so.2". Plenty of each but never combined as libpq.so.2.
Tom