PG 7.3.4 VS PG 8.0.3 Problem

I am having an issue with 7.3.4 vs 8.0.3.

I have done a simple conversion of one of my databases from 7.3.4 to
8.0.3. I used the 8.0.3 pg_dump to dump the database and load via
psql 8.0.3.

However, I am having a problem. I have a query that our application
generates that is returning different results back to our application.

When I connect to a 7.3.4 database, the query returns 0 rows and a
sqlca.sqlcode of 0

However, when I connect to an 8.0.3 database, the query returns 0 rows
and a sqlca.sqlcode of 100.

Why is the 8.0.3 database returning a different code? Our application
is checking the code returned, and since it is getting a 100, it is
not performing as expected (as compared to our 7.3.4 production
system).

Anyway, the only thing that has changed in the environment is the
PostgreSQL db. The Application and odbc drivers are all the same.
Can someone please enlighten me as to what is going on?

Thanks,

Chris