File exists on remote server

I am trying to get my webserver to check if a file exists on a remote server:

location of file: \\remote\foldername\filename

c# code

if(File.Exists("\\remote\foldername\filename"))
{
\\ do stuff
}

given that the webapp authenticates through windows, impersonates the NT users and that all the user have been granted access to the Framework folder (and sub-fodlers) and granted access to the remote folder, I still am not able to verify the existance of the file from the webserver. Btw, it works great when I am debugging it on my local machine.

Any clues? Thanks ...