I've had this happen once before, a long time ago, and then i lived another place.
I start diablo 2. It can happen at any time, startup or in the middle of a game. What happens is, suddenly, the game operates in like 1 second lag intervals. I.e., every 1 second, the game updates itself. This makes it impossible to play, especially on hardcore which is what i play.
But here's whats even stranger. I quit the game and start websurfing instead. Now the mechanism continues there! Everything i do, open new tab, update tab, open news article, surf d2jsp, whatever.. it happens in 1 second intervals. Then it randomly stops, i can try playing again, and it's random if it happens again or not.
Whatever can cause such a strange occurrence?