Have you seen the meaning what it conveys when you type a wrong password for a user name.

"Username and password do not match. (You provided ssuresh83)"

sometimes it means string match "username and password should be same".

what is the otherway they can rewrite

your views on this.

"Your Username and Password pair do not match our records" (CollegeHumour do something similar)

or
"Your Username is Wrong" / "Your Password is Wrong"

or put together
"Your Username or Password is Wrong"

or maybe somthing more helpful like
"Your Username or Password is Wrong, or may be typed incorrectly, please retype them and try again"

James
   i go with your first message
"Your Username and Password pair do not match our records"

Yes, that's my favourite too :)