[windsurfer]

You might be overzealous with your bot blocking. I'm being told I'm actually a robot:

    you appear to be a bad robot
    check out the rules for robots. thanks.

[wjamesg]

I believe I've had this happen when using a VPN service (though I could be mistaken)

[Pyramids]

Same here, are you using RES or anything else which might increase request volume?

[jaredmcateer]

I use RES, not having any issues.