VPN won’t disconnect after Outlook 2k3

I have two users with WinXP SP2 and Outlook 2K3 in the field who vpn to our network to use their email. The problem is, they can’t disconnect the VPN after opening Outlook 2k3 and have to reboot to surf the internet. It looks like the disconnect command worked and the 2 flashing computers disappear but if you do an IPCONFIG, you see you still have a VPN address assigned. Also, if they open outlook (cached mode) it automatically tries connecting via VPN even if they just want to use it offline. I have about 20 other users in this same setup who operate just fine so it’s not anything on the server side.