How to log in wireless router settings

Hi guys

I am using (ZyXEL NBG-416N) wireless router,
usually click on the browser and type: 192.168.1.1 then log in widnow : admin , passweord 1234,
since yesterday I was trying cant log in, just show me the page loading and white content.. not show anything..
I tried with IE, firefox, and chrome, all the same resutls,
what to do to log in? any more options?
regards.