calling function with String resolves as "Unknown" instead of varchar

I'm calling a function with the following signature:

create or replace function
usp_affectedproduct(integer, integer, varchar) RETURNS
int as ...

I'm calling the function with something similar to:

String query = "{? = call usp_affectedproducts(?, ?,
?)}";
Connection conn = null; CallableStatement s = null;
try {
conn = getConnection(datasource);
s = conn.prepareCall(query);
s.registerOutParameter(1,Types.INTEGER);
s.setInt(2,qualityid);
s.setInt(3,submitid);
s.setString(4,products[x].getName());
s.execute();
} catch (SQLException e) {
throw e;
}finally{
<clean up stuff ...>

When I run this, I get an SQLException stating:

function usp_affectedproducts(integer, integer,
"unknown") does not exist

I've also try s.setObject(4, aString, Types.VARCHAR),
also to no avail. I've tried using a
PreparedStatement instead of the CallableStatement -
again, without success.

Any ideas? I'm running 7.4.1 on RedHat 8.0 with JDK
1.4.1_01.

Thanks in advance

=====
The only "dumb question" is the one you were too afraid to ask.
________________________________________

Check out RouteRuler - Free software for runners, cyclists, walkers, etc.
http://routeruler.sourceforge.net
________________________________________

__________________________________
Do you Yahoo!?
Win a $20,000 Career Makeover at Yahoo! HotJobs
http://hotjobs.sweepstakes.yahoo.com/careermakeover