Could it be that after several good beats you tend to play a little looser or more aggressive with hands you normally wouldn't, and therefore get more "bad beats"? Not saying there's anything you could have done here, but for me at least, I find that when I'm doing well I tend to play more mediocre hands, which in turn knocks down my bankroll to around the original starting point......
Wow, just took the first step (admitting I have a problem). Soon I'll be knocking on everyones door to whom I gave a bad beat and asking for forgiveness.