Verification Code in Firefox repeatedly throws error on correctly entered code

Verification Code in Firefox repeatedly throws error on correctly entered code

I have seen this issue on the forum, and it keeps being said that there is no issue because support can't reproduce it.  Or the other one is to use a "supported" browser.  I understand there are a lot of browsers, but keeping up is crucial to the success of your applications, Zoho.  My client is using Firefox 10.0.1 and she has sent me multiple screenshots of the verification code repeatedly failing to recognize a correct entry.

I provide those screenshots:
FORM 1 shows a correct code being entered after an error on a previous correct code
FORM 2 is just after photo 1 was submitted, you see another error has occurred and she again has entered the new code correctly and is about to submit again.
FORM 3 is the 3rd error that has occurred after yet another correct code was submitted.  You will see there are no other problems on the form.

Please fix this issue.  Without Captcha, my forms are just sitting ducks for spammers.
Thank you