You may need to manually download and install the newest version. www.getfirefox.com is the best place to go. Just download Firefox 10.0.2, then install it over your current install.

Thanks Tylerdowner for the reply. In old days it used to update itself, i love getting my firefox updated that way. Anyway i will download and install latest version now :P

Firefox should auto update, sometimes the system doesn't quite work as expected however. When it does that, the easiest solution is to download and install a fresh copy.