I just fired up my Firefox 3.6.24 portable version and it's working fine with script shield.
@speedypc, Many people continue to use 3.6 for a variety of reasons one of the most important being website compatibility. Many .edu, .gov and private institutions still only support 3.6 and will continue to do so b/c Mozilla still supports 3.6 and also b/c Firefox ESR is not up and running yet.