KFURGE.. I have never been able to add a user thru the web interface using any of your custom firmware.. is it a problem on my router ??

I use the web interface and it allows me to change the setting to user based access.. but then when I click on add user.. it allows me to enter username and password etc.. but when I click on apply.. it always fails and a error box pops up.. Somehow this problem goes away when I use the Asus Firmware..(both 4.6 and 7.8)..

Why could this be happening??