Access Denied

Today morning i witness a strange issue while login to NAV Client.

I entered the server IP, Username, Password and i selected the DB which i am going to login, and then pressed OK button, immediately error message "Access Denied" appeared in the screen.

But, i can login to SQL DB through SQL Management Studio with the same NAV username and password. Did anyone come across with this issue? I am clueless what is wrong with the NAV client.

Please help me to resolve the issue