Game freeze sometimes

Sometimes game freezes for me after I make move. Clocks are stopped, my last move is on board. After I refresh page (browser asks if I want to leave page) game is continued, my clock is running as I never made move and my last move (one after which clock stopped) is not registered.

Also happens to me. And it's a shame because I could've won against a much stronger opponent:



I lost 2 min 20 sec thinking that he's thinking :)