Can you fill me in on where this happened and what your input was? I'm not able to replicate your problem. The input for the number of days/months/years should be numeric, which I should probably not there somehow. Is that your problem?
I also just got a captcha with an umlaut ... not very convenient on my keyboard.
And re: your post below, yeah, try the cache - I just added a feauture called "Testing validations" with no problem.