BEFW11S4 V.4 Linksys Router Problems?

Ive never had problems with my router but recently when i tried to change some settings it wouldn't let me save the changes because it says I need to enter a user name and pword I know that the default pword is "admin" but it doesn't except it i enter it 3 times and after the third time it takes me to the "401 Authorization Required" error screen. I have tried many things to fix this problem turning off my router resetting it, and even doing a hard reset, i also tried to upgrade my Firmware but nothing seems to work. If any one can help me i would be really thank full