Finally fixed the problem after a factory reset....... Luckily I haven't setup too much settings.

go720er wrote On the Backup & Restore screen of your router web page, go down to Factory Default Restore. Click ONLY the Restore button. This will restore your router to the factory defaults values,...

Actually this is my brand new router with default settings. Just preformed an upgrade before use. I'm not expected it will getting worse after that. Anton L.Z. wrote hi zeuscho, did you restore the...

I tried most of the browsers: Chrome/Firefox/IE...... but seems are the same result. (clicked save -> settings turn red with no error message).

Once I click save, the font colour for settings just turn red and nothing happened. And the settings not saved. uutommi wrote to zeuscho,i am not following you, any problem with the red color? but...

Refer to my previous post. Anyone have the same problem for the parental control? http://forum.tp-link.com/showthread.php?98970-Archer-C5400-parental-control-problem