disconneted no supported authentication methods available(server sent :public key)

Hi,

I am working on EC2 but i think by mistake i had remove read write access for bitnami folder ... so for ssh key also i dont have read write access to access my server using putty ...it asks for login name but when i type bitnami it throw error disconnected:No support methods availble (server sent public key)

so can anyone plz help mi out in this problem to access the my sever .. i also tried using my backup key but this will not work ....

Thanks in advance ....