error {"Logon failure: unknown user name or bad password.

culd u explain

if i am using the application  frm the webserver itself with its local databse i dont get any error
it wrks fine
i get this error onlly when

my web server is differnet, databse server is another and client sytem is different
now i getthis eror when i am trying to save file frm databse server using application frm web server on client system
 
<system.web>
<identity impersonate="true" userName="mydomain\myusername"
password="mypassword" />


i have used this in web config
 
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