Can't open facebook and twitter

pls someone help, I'm using windows 7 and mozilla firefox
and something weird happen
I can't open facebook or twitter
this is like my friend's PC

so this is what happened

1st my PC is fine, then I go to my friend's home to copy some musics, and he told me that his PC can't open facebook or twitter

after that I go home, and then I move my friend's PC musics, from my external HD to my PC

after that I cannot open facebook and twitter, I try mozilla, IE, google chrome

nothing works

so I try this, restarting my computer, it works, but next minutes I can't open again

I try to disable enable connection, works too, but just like before, I can't open in next minutes

I scan my PC with kaspersky, no threats

every web is fine, except facebook and twitter

pls help me, I'm so confuse