Steps to reproduce :
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1. Uninstall all jdk/jre and remove "Sun" folder in user home
2. Make sure IE setup the right proxy . In IE LAN setting , set proxy server to : webcache.sfbay.sun.com:8080 , and check "Bypass for local addr" and check "Use the same proxy server for all protocols"
2. Install jre1.5.0_06 (build 1.5.0_06-b05)
3. In control panel , set Network Settings as "Use browser settings"
4. In control panel , check on "Enable tracing" "Enable log" "Show console" , and in "Default Java for browsers" ,only check on "Microsoft Internet Explorer".
5. Launch the "host not match" test using:
   jre1.5.0_06\bin\javaws http://sceri.prc.sun.com/~yl153753/https/https_hostnomatch.jnlp
   In "verified" security dialog ,don't check "Always" and click "Run".
   In "Warning - Hostname Mismatch" warning dialog , click "Run"
6. java.io.IOException thrown , and in console , can see
STATUS: HTTPS_HOSTNOMATCH EXCEPTION
java.io.IOException: Server returned HTTP response code: 400 for URL: https://usna1.central/index.html
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(Unknown Source)
at java.net.URL.openStream(Unknown Source)
at HttpsTest.main(HttpsTest.java:51)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at com.sun.javaws.Launcher.executeApplication(Unknown Source)
at com.sun.javaws.Launcher.executeMainClass(Unknown Source)
at com.sun.javaws.Launcher.continueLaunch(Unknown Source)
at com.sun.javaws.Launcher.handleApplicationDesc(Unknown Source)
at com.sun.javaws.Launcher.handleLaunchFile(Unknown Source)
at com.sun.javaws.Launcher.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

No exception thrown if run with jre 1.6.0 (build 1.6.0-rc-b61)