Are you logged in when you do this?
Yep. Also sent a message to Ryoko about it. It's just annoying and it takes a while to find posts.
For example if I search for your posts, and go to page 2, you'll get the error.
I believe this all has to do with search flood interval limits. Really though, its 5s. Which means to hit this error, your clicking to other pages within the 5s limit. I've reduced it a little bit; let me know if you see any difference.
For a guest account, its some 30s.
The reason I don't see it on my account (Nor would any admin) is because we ignore the flood limits on the board.