I note that some people are having trouble with the captchas.
There are two words which you have to type: one of them is the true test, the other is actually using you to help convert scanned text into digital form. In other words, they get you to type in one word and they check it against the graphical image; then for the second graphical image, you are actually typing in text for e.g. some piece of a scanned book which could not be translated into digital form reliably. The second word is a sort of crowdsourcing.
You obviously have to get the test word right, but for the other word it doesn't matter what you type. I tested this and I found that for me the second word was the true test; for the first word I typed in some rubbish and I still got through.
Sorry this is a bit long-winded, but try to just get the second word right and see what happens.