I found that a MIDlet will silently die on Nokia N90 and 6680 when trying to read the content of an HTTP "302 Found" server response.
Here is a small code showing it :

import javax.microedition.midlet.*;
import javax.microedition.io.*;
import java.io.*;
import javax.microedition.lcdui.*;

public class Test
extends MIDlet
  private static final String URL = "http://server.domain/your_script.php"
  protected void startApp() throws MIDletStateChangeException
    Form f = new Form( "Test" );
    String response="";
    try {
      HttpConnection con = 
        (HttpConnection)Connector.open( URL, Connector.READ );
      InputStream in = con.openInputStream();
      InputStreamReader reader = new InputStreamReader(in);
      char content[] = new char[1024];
      int len = reader.read( content, 0, 1024 );
      response = String.valueOf(content,0,len);
    catch( IOException e ) {}
    f.append( new StringItem("Reponse : ", response, StringItem.PLAIN) );

  protected void pauseApp() {}

  protected void destroyApp(boolean arg0) throws MIDletStateChangeException{}
And here is the server-side PHP code to generate a HTTP 302 reply with content :
header('Location: http://www.forum.nokia.com/' );
echo 'plop';
It was REALLY hard to find out why my much more complicated app kept on crashing...
Isn't that part of the HTTP standard to send a content together with a 302 reply ?