uanble to login to cisco Router

hi all.
i’m trying to backup the running config to a Tftp server and test that .i have backed up that file succesfuuly ,to test that ,i disabled the enable password and exit from the Router .
When i again gave the enable password ,it is saying that password not set ..
I’m gone ,what to do now ..
i have set the service password-encryption running on that earlier ,then disabled the enable password .I’m able to login into the Router ,when i hit the enable and hit enter ,it says that no password set and exits .
it is not letting me in now ..
the model of the Router is Cisco 2511 …
i have the backup config file ..
i need to login ,what to do now ..
please help .