OS - All
Browser - Mozilla1.7 +

Steps to reproduce -

1) Install jre/jdk 1.6.0

2) Make sure that <deployment_user_home>/security is clean i.e. there should not be certificate store exist,if any remove it

3) Rename the <jre_home>/lib/cacert file. Since you are renaming the cacert file inside <jre>/lib directory make sure that JRE is locally installed on the machine

4) For windows
   Copy /net/sqe1/quality1/deployment1/deployment_mustang_int_ws/deployment/src/deployment/keystore_mozilla/lib/jss3.dll to your Mozilla home directory
   Copy
/net/sqe1/quality1/deployment1/deployment_mustang_int_ws/deployment/src/deployment/keystore_mozilla/lib/jss.jar to <moz_home>/jss

5) For Unix,
   Set "MOZILLA_HOME" env variable to Mozilla home directory
   Copy jss.jar to this <mozilla_home>/jss
   Copy
/net/sqe1/quality1/deployment1/deployment_mustang_int_ws/deployment/src/deployment/keystore_mozilla/lib/libjss3.so to Mozilla home directory

6) Make sure that "Use Certificates and keys in browser keystore" under Advanced->Security in Java Control Panel is checked(by default it should be checked)

7) Run the signed applet
https://sqe-jpi-01.sfbay.sun.com:8443/tests/https/pluginhtml-default/GP.html.
Make sure you see that the jss libraries are loaded on the java console

8) Accept the security messaged coming up from the browser side and the Java Security warning dialog should indicate "The security certificate was issued by a company that is not trusted"

9) import the following certs under Certificates -> Authorities in the browser
  /net/sqe1/quality1/deployment1/deployment_mustang_int_ws/deployment/src/deployment/keystore_mozilla/lib/sun_gte.crt

/net/sqe1/quality1/deployment1/deployment_mustang_int_ws/deployment/src/deployment/keystore_mozilla/lib/sun_test_ca.crt

10) Run the above signed applet again. This time again the Java Security warning dialog indicates "The security certificate was issued by a company that is not trusted"

This is not right. After importing the certificates, "the Security warning dialog should indicate that the security certificate was issued by a trusted company"

The above problem is seen acroos all platforms.