Gift Certificate Invalid Text

Hi, all. I have posted in a thread about this here:

http://www.zen-cart.com/forum/showthread.php?p=811199#post811199

and not had any luck so thought I'd go a different route. When people click the redeem link in a GV mail, it redeems their code and then they try to enter it again on the checkout page because they don't realize that it's been redeemed. I tried to change the link in the mail, I changed the files that were indicated in the above linked thread I posted in, but nothing changed. I tried the override folder, then tried overwriting the default file, nothing changed. So, I decided to go another route and change the error message. I found the error message in languages/english/gv_redeem.php. I changed it and still, nothing happened. I am at a complete loss here. I've tried everything I can think of to change this and make it easier for people to understand what they need to do and stop the e-mails my client keeps getting in regards to this and I just can't make anything happen.

Help? Please?

I don't generally bump my threads, but I've never had this much trouble getting help and it's been almost a week now. Can someone please help me figure this out? I have a client who is losing patience and I just don't know what else to do.

Thanks!