Do you frequently open "All" pages? If so, that's the reason since AFAIK it's intentional configuration set by theymos. Still, it happens few times to me, but usually i just need to wait between 5 - 15 second.
I would try different circuit if i were you.
No, I don't open it more often than before, the only times I've seen this message before was on this "all" link but for the past few days I see a difference, message is coming more often while reading topics, without clicking the "all" link and when I log in today I had to wait for a while, the 5 sec screen kept refreshing a few times.