[TYPO3-english] back end unable to login

[Girmangus Hailu]

i'm using typo3 4.5.2 and typo3 back end not allowed me to access it. on my
local machine works correctly but not  on the official domain. the Mysql Server
version: is 5.0.67. and the error shows me typo3 backend is as fellow

Your login attempt did not succeed

Make sure to spell your username and password correctly, including
upper/lowercase characters.

 but i'm sure my username and password are correct and i also try to create
another user using the /install/ but not allow me to create on the mysql
server.