Cisco Secure ACS

Hi,

i am having come problem working with Cisco Secure ACS. My company had recently purchase the Secure ACS appliances and i was suppose to put it in a trial testing before the actual implementation.
I have build and configured windows server 2003 R2 Domain controller with active dicrectory, dns and DHCP service running within. On top of that, i also have a layer 3 cisco 3550 switch to accomodate my testing equipment including domain controller, one client PC (joined to the domain) and cisco ACS.

On my domain controller, i have configure 2 user account (FinUser and ProUser)and 2 self defined user group namely FINANCE and PROJECT and assign one user under each group. For my DHCP, i have 2 different scope(192.168.1.50-254 for FINANCE and 192.168.2.50-254 for Project) prepared and activated one scope for each of the department.

I joined my client PC to the domain which i had created and configure my ACS(Radius) to use external database (from my domain controller ) to provide authentication.

I have also configure selected switchport on my layer 3 switch to work with 802.1x.
within it , i populated 2 Vlan to simulate Vlan for my finance and Project department.

On my ACS, i have made the necessary configuration including the group mapping for my external window database.

The problem starts here, when i log into windows, i am expecting to see the pop up windows "Enter Credential " by the ACS server by double clicking on the information dialogue at the network connection icon and it does show up. I had manage to get an ip address when i login using the user account for finance and ip address shows "192.168.1.50" which is correct.

After which, i unplug the cable from the switch port to simulate looging off or shut down and plug it back into the same switch port, instead of the dialogue prompting me to re enter the credential, it just get connected and gives me the IP address.

I unplug the cable and connect  to another switchport (same client PC), this time it prompts me, but when i use the login credential of the Project user, it does not issue my IP address on the correct DHCP scope, meaning that instead of getting 192.168.2.50, i still get 192.168.1.50.

i find that the PC is caching the previous IP address and i had to manually go to the registry under "HKEY CURRENT USER" -> "Software" -> " Microsoft" ->"EAPOL"-> "UserEapInfo" to delete the key before  it will allow me to reconnect with the "Enter Credential" prompt windows and assign the coressponding IP address based on the defined scope.

How can i prevent from doing the manual work over an over again, i need to get it automated that the IP caching is not taking place so that anyone who plugs into the switchport have to be authenticated and not once u manage to log in once and u can continue to used it until the cache flush off.