I have the BEFSX router and found that the latest firmware is neither the best nor the most stable. I spent hours searching for firmware and finally found a thread on another forum
http://www.dslreports.com/forum/rema...flat~start=220 - this relates to my own router, but if you work backwards you should find something relating to your model?
I also found a very helpful user who provided links to old firmware which I have found to be the most stable for my requirements.