Changing Domains Name of the Shop

[prestamoi]

I created a Prestashop store to "DOMAINS.COM", i install it and start to work on this no problems so far, then i realized that i wanted to have "DOMAIN.COM" without "S" as my shop an i put the domain to go on the same folder i had the first domain... front office is working , no problems there.... then when i try to logging to the back office is impossible i don't get any errors I just get "/adminfolder/login.php?redirect=index.php" and it does not logging, so i when back to the old domain and change the preferences on the back office for the shop url and everything and still nothing! what can i do?