There could be multiple issues ranging from:
1. Vulnerability(super User) is set for alias with the account that keeps logging in.
2. IIS has cached the login on your machine.
1. Go into the Priveledges section of the Risk Fabric console and insure that vulnerability (super user) is unchecked for accounts that won't login.
2. Right Click your internet browser and "Run As" the domain account you wish to log in with.
3. If that still doesn't resolve. Clear browser cache and cookies and try again.
4. If that still doesn't work, reset IIS server.
5. If that doesn't work, make sure domain accounts you want to log in with have READ access on the Risk Fabric web server directory on the IIS server.