Nah. You can whiff on grabbing HITs that are up even if you're not sending any other requests. Not sure if something is broken, or if it's just throttle on throttle, but it's the worst thing about the worker site.I'm guessing they put in some new variable that gets tripped to ON when you request a HIT that isn't currently available, and then mturk reports an error for any page you request (for some set time). That fits with my experience, at least.
Thanks to all contributing!