The only currently supported versions are 3.6.18 and 5.0. Firefox 5.0 was an upgrade from Firefox 4.0.1 and includes security updates that Firefox 4.0.1 does not include. All other versions contain security issues and should not, for your own protection, be used.
You need to update the following. The Plugin version(s) shown below was/were submitted with your question and is/are out of date. You should update to avoid known security issues with the version(s) you have installed. Click on "More system info..." to the right of your question to see what was included with your question.
Adobe Shockwave for Director Netscape plug-in, version 11.5
Adobe PDF Plug-In For Firefox and Netscape "9.4.3"
Next Generation Java Plug-in 1.6.0_18 for Mozilla browsers
Check your plugin versions on either of the following links':