Insert fails from VB only when table is empty...?

I am brand new to pgsql... J  I have a VB program inserting records into a fairly simple table (without a PK) and I notice that when the table is empty I get a "row out of range" error.  This only happens when the table is empty.  If I insert a record from psql then run the program everything is fine.  Any ideas as to what may be wrong?

Thanks,

Kevin