It uses jsonp to talk to the twitter api, so if its a rate limit, its on your own ip, are you in a large company or uni by any chance? Otherwise it might just be a slow connection, you dont really know when a jsonp call has failed, so you just have to time it out after a while and assume thats what happened, happens to me every now and again when using it from a phone. If its none of the above, please send me a message using the sites contact form, it tells me a lot about your browser in the process and I can try and replicate the problem.

Try changing the case of the letters, I had the same issue.