Security Erros

[Digi]

Hi, today, i was not able to register new user on my PS, after filling all information when i click register button that return page can not be displayed but i got mail from my shop that i've registered.
When i try to login admin panel that show security warning for removing install folder (I've ALREADY DELETED IT BEFORE) and change admin folder name to something else (ALREADY DONE IT BEFORE)
don't know what is the main problem if you know then please help meeee
i'm using prestashop 1.2.5.0