Problem using libpsql.a

I have an application that forks of a process and is updating a table in my postgres database.  When
I have the parent process query that table to see how much has completed I get weird results.
Sometimes it works, sometimes it core dumps, and sometimes I get back a NULL results structure.  But
if I type that same query into my psql window, I get back the correct results everytime.  Currently
I don't do any type of locking on any of the tables.  My question is should I be doing some locking
and why is the query using the psql command prompt working and my direct call in my C code isn't?
Thanks!!
---------
Chris Williams
Sterling Software
Rome, New York
Phone: (315) 336-0500
Email: chris_d_williams@sterling.com