The latest Firefox is 3.0.5 and it is in the repositories for VL 5.9 and VL 6.0. You should make sure you have the Patches repository enabled. It wasn't by default in 5.9 and that actually was a bug. If you don't have Patches enabled then you most certainly have a system with LOTS of security vulnerabilities.
We aren't packaging the Firefox 2.x series anymore. The latest in that series is 188.8.131.52.
eMachines EL-1300G desktop, 1.6GHz AMD Athlon 2650e CPU, 4GB RAM, nVidia GeForce 6150 SE video
CentOS 6.5 (will try VL64-7.1 soon)
Toshiba Satellite A135-S4727, Intel Pentium T2080 / 1.73 GHz, 2GB RAM, Intel GMA 950
HP Mini 110 netbook, 1.6GHz Intel Atom CPU, 2GB RAM, Intel 950 video, VL 7.1