Integrated Windows Authentication showing wrong loggedin user

I have an asp.net 2.0 application running on IIS 6.0. I am using Integrated Windows Authentication. Some users have two network accounts, a personal account and an administrative account. The problem I am facing is that sometimes when they are logged in on the client side using their personal accounts, the logged in user appears at the server side as the admin account. I am retrieving the logged in user network id using System.Security.Principal.WindowsIdentity.GetCurrent().Name. I suspect that their admin credentials are being cached somewhere and passed instead.