Windows 7: cannot login/sign in yahoo mail, skype and even yahoo messenger

im not sure the problem with the browser or the connection, but im pretty sure there is something wrong with my internet conection.

i unable to signin my yahoo messenger, skype and even cannot load to yahoo mail website. but i still can surf other website normally. i noticed that some of the page that required password are unable to load. the will be an error that ask to check the intrnet conection. im using LAN connection. i tried to login yahoo mail, and signin skype and ym by using my friends pc in my home and i can login/singin without any trouble. we using the same internet connction.

i already reformat my laptop cause i thought there is laptop problem. but there is still no luck. same problem still occur. i scaned my lappy with updated antvrus (btdefender) but no virus detected. i also tried unable the firewall in my system but no changed. i still face the same problem.

i realy hope that someone can help me figureout this problem...

Try to disable your firewall and your Anti virus.
Good luck:-)