Cookie problem in prestashop trying to enter the admin

[Agustin199]

Iam using prestashop 1.2.5.0 , when i tried to enter to the admin y type the user and the password. But the webapp instead of going to the admin goes to the login .
I think it may be a cookie problem because after i enter the data in the login the application shows me a link to the admin and then redirects.
I have tried the following things:
-cleaning smarty cache (cleaning except index.php the folder tools/smarty/compile ).
-Commenting on init.php and login.php the lines where they created the cookie to create my own cookie with location /webappname/adminfolder/
-Cleaning all the cache of the browsers and using all the browsers.
If someone could help me .