I mucked about a bit with the myquiz module and got the english language working on my site (have not touched the other language files). Tidied it up a little to suit me if its of any use to you you can see it and download it from my test site at http://horsegenie.com/testsite/

Have only tested it on my site so cant say if there are other probs with it. If you find any let me know and can see if I can fix it.