Error on opening HTTPS connection (java.net.SocketException: Unknown system state.)

Hello all,

I'm having a problem when attempting to open an HTTPS connection on
the '400. I've created the following code to replicate the problem:

URL url = new URL("https://my.test.server/test";);
URLConnection conn = url.openConnection();
BufferedReader br = new BufferedReader(
       new InputStreamReader(conn.getInputStream()));

The test server will simply respond with a test message, which works
as expected from any PC I've tried, but fails when run from the AS400.
The exception thrown is:

java.net.SocketException: Unknown system state.

java/lang/Throwable.<init>(Ljava/lang/String;)V+4 (Throwable.java:94)
java/lang/Exception.<init>(Ljava/lang/String;)V+1 (Exception.java:42)
java/io/IOException.<init>(Ljava/lang/String;)V+1
(IOException.java:47)
java/net/SocketException.<init>(Ljava/lang/String;)V+1
(SocketException.java:36)
com/ibm/as400/ibmonly/net/ssl/SSLSocketImpl.startHandshake()V+1
(SSLSocketImpl.java:967)
com/ibm/as400/ibmonly/net/ssl/SSLSocketImpl.write([BII)V+13
(SSLSocketImpl.java:428)
(the rest of the message cut...)

This is interesting to me as the exception appears to generate from
the com/ibm/as400/ibmonly/net/ssl/SSLSocketImpl class in the
startHandshake method. I am unable to find any documentation or source
code for this class, and am not quite sure where to look next.

Is there some configuration on the '400 I have overlooked? I can't
imagine much configuration need to be a Java SSL client (at least not
on any other platform I've tried).

Any suggestions appreciated.
Carl.

P.S.
OS V5R1
AS400 java version "1.2.2" (Yes, really. :( I've been working on
having this updated)