HTTP Error 500.19 - Internal Server Error -- IIS when accessing shared by specified user

I created a virtual directory (on Server 1) to access a shared location ( share is on another server ). to give the URL as http://server1.com/alias The shared location contains few folders.

Through my another application ( located on server1), i need to access URL http://server1.com/alias/folders

Instead of using pass through application, i used specific user credentials to connect to shared location. Also verified that the user has full access to shared location.

But when accessing the URL http://server1.com/alias/ i get below error.

HTTP Error 500.19 - Internal Server Error
The requested page cannot be accessed because the related configuration data for the page is invalid.

Module IIS Web Core 
Notification BeginRequest 
Handler Not yet determined 
Error Code 0x8007052e 
Config Error Cannot read configuration file  
Config File \\?\UNC\server1.com\alias\upload\web.config 
Requested URL http://server1.com/alias/
Physical Path \\server2\\share
Logon Method Not yet determined 
Logon User Not yet determined 
 Config Source
-1: 
    0:

Instead of using specified user credentials, when i specify my windows login credentials , then there is no issue in accessing the URL. Please help