Daniel Arnold wrote:
So it is no surprise that en.wikipedians do make less failures on english captchas with undefineable letters.
I hope you can track and maybe solve the problem now (people bug our Wikmedia-OTRS quite often with captcha problems).
In other capthca related news reCAPTCHA (http://recaptcha.net/) is now available for Mediawiki. Might be an option for some people.