i already find the solution for my problem. i hope this can help you all too. Check whether you have changed your domain name.
Go to Settings -> General settings
Check WordPress Address (URL) and Site Address (URL)
The default should be http://yourdomainname.com
DO NOT add or change to something like http://www.yourdomainname.com
I have this problem since the first time I log in to wordpress. I hope someone can answer this thread
