Why can't I follow more people today?

Twitter is telling me I've reached my follow limit for today, but I have only followed about 60 new people today. I'm well over the 2000 follower limit (follow 33,000 people with 34,000 followers) and this behavior is inconsistent with my experience in the past. Typically I can add betweet 600-1000 people every day. What's up?