When I moved from 6.5 to 7.1.1 I decided to change the cookies name and looks like that was a bad choice.
Now many users cannot connect if they don't erase ALL cookies on their computer (well, they can erase ALL cookies from my site, but most of the users have no idea on how to delete all cookies, so I'm telling them to delete ALL).

Is there any way I can revert that choice and put back my old cookie name?
How?
Thank you

In the advanced section of the Primary Settings, you'll see where there custom cookie prefix is set. The only problem with changing this now is that it's probably going to cause problems with users that have been able to login, and they'll have to delete their cookies.

People that are having trouble logging in should just be able to use the "My Cookies" link down in the footer bar to delete them.

Rick,
I tought that if the user just use the My Cookies all will be fine, but it's not. I could not reproduce the problem here on my end, but I have a large population of users that are sending me e-mails complain that they could not login on the forum...
I understand that changing the cookies now would pose a problem for those users who ARE login in fine, so I'm kind on a corner here...

Honestly, either way, one set of users will be in a pickle; the only real way to get around this is to write up how to purge cookies from:
1. The Forum
2. Their Browser

And wait for them to do so; you can't just wave a wand and do it for them, the only thing you can do is cater to the larger set of users.