[Armin]

I used to experience this constantly, when I went to bed a bit later than I do now. I used to always browse the SJGames forums before bed, and I'd constantly find the site completely unresponsive for just a few minutes. I don't believe I ever had to wait more than five minutes for it to come back, though.

I always just assumed they had some automatic server maintenance job that ran around then, and was intensive enough to hang the server for a few minutes.