admin tool bar and password problem

I am facing problem from last 10 days, i google for problem solution,try to find out on wordpress if any have this issue but some of them find but not resolve. The problem is

Suddenly i got a problem my admin tool cannot show while i am on my website, in profile it is click, my password cannot saved in though its correct but every time i put correct user and pass and it show again and again login page. i disable all plugin, then delete all plugin, but problem not resolve. change even themes but still problem is not resolving . change password through phpmyadmin. Even that theme was working perfectly but suddenly these problems occurs. Kindly help me.