Can't connect JNDI using LDAP/SSL

[Ian Harding]

I have created a certificate on a directory server, and imported it into
the Java keystore on my client machine. Listing the keystore contents
includes the certificate data:

Alias name: testpc18
Creation date: 01-Sep-2005
Entry type: trustedCertEntry

Owner: CN=testpc18, DC=cornwall, DC=company, DC=com
Issuer: CN=testpc18, DC=cornwall, DC=company, DC=com
Serial number: 6137514bb844f8b84515cfc29f48d742
Valid from: Thu Sep 01 13:15:54 BST 2005 until: Wed Sep 01 13:20:51 BST 2010
Certificate fingerprints:
MD5: 31:8E:C0:42:86:7D:42:27:63:26:91:A8:41:95:25:C2
SHA1: 01:2C:56:1ED:559:5B:93:A7:B2:A0:F6:72D:A7:60:B2B:89

I use this client code (based on a sample found on the web):

Hashtable env = new Hashtable();
String adminName =
"CN=Administrator,CN=Users,DC=CORNWALL,DC=COMPANY,DC=COM";
String adminPassword = "xxxxxx";
String ldapURL = "ldaps://testpc18:636";
String keystore = "C:/Program Files/Java/j2re1.4.2_03/lib/security/cacerts";
System.setProperty("javax.net.ssl.trustStore",keystore);

env.put(Context.INITIAL_CONTEXT_FACTORY,"com.sun.jndi.ldap.LdapCtxFactory");
env.put(Context.SECURITY_AUTHENTICATION,"simple");
env.put(Context.SECURITY_PRINCIPAL,adminName);
env.put(Context.SECURITY_CREDENTIALS,adminPassword);
env.put(Context.SECURITY_PROTOCOL,"ssl");
env.put(Context.PROVIDER_URL,ldapURL);

try {
DirContext ctx = new InitialLdapContext(env,null);
....

At runtime, the last line throws an exception
"javax.naming.CommunicationException: simple bind failed: testpc18:636
[Root exception is javax.net.ssl.SSLHandshakeException:
sun.security.validator.ValidatorException: No trusted certificate found]"

The client does have the trusted root certificate for the directory
server (running Active Directory on Windows Server 2003 SP1, if that's
relevant). I am definitely passing the correct keystore to the client
app, and the certificate has definitely been added to it.

Can anyone help me spot what I'm doing wrong?

Thank you,
Ian