FF 5/6 do not react to java properly

Question

In several websites, some button in popup windows do not react, or not complete the expected action. For example, when"Delete" is pressed in a message window, the message is deleted, but the window does not close.
With internet Explorer, or Opera (latest) all is fine as expected. Also, I did not have this problem prior to upgrading to FF5.
I suspect that it has to do with Java stuff. is something missing in my software?
One site is given below.

Answer 1

Firefox versions 4.0, 4.0.1, 5.0, and 5.0.1 all have security and stability issues that have not and will not be fixed in those versions. Beginning with Firefox 4.0, all new versions supersede/supercede the prior version and the prior version is "abandoned" in regards to updates and support. Using any of the versions listed makes your system vulnerable. See the security issues fixed since Firefox 4: https://www.mozilla.org/security/known-vulnerabilities/firefox.html#firefox6
If you will reply with specific reasons that you do not want to update to Firefox 6.0, a volunteer here will try to help your resolve any issues.
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Not related to your question, but...
You need to update some plug-ins:
*Plug-in check: https://www-trunk.stage.mozilla.com/en-US/plugincheck/
*Adobe Shockwave for Director Netscape plug-in: [https://support.mozilla.com/en-US/kb/Using%20the%20Shockwave%20plugin%20with%20Firefox#w_installing-shockwave Installing ('''''or Updating''''') the Shockwave plugin with Firefox]
*Adobe PDF Plug-In For Firefox and Netscape: [https://support.mozilla.com/en-US/kb/Using%20the%20Adobe%20Reader%20plugin%20with%20Firefox#w_installing-and-updating-adobe-reader Installing/Updating Adobe Reader in Firefox]