If you build the driver from the aolserver sources, the shared library will be called nspostgres.so. The reference nsd.tcl file for openacs references the postgres driver library file as postgres.so, so you'll need to change the name of the library file or change the reference in nsd.tcl. Also, I haven't looked at the driver in aolserver 3.1, but you'll probably need to add -DFOR_ACS_USE to the CFLAGS directive in the nspostgres makefile. By default, they probably don't include the Openacs extensions to the postgres driver.
