windows 7 and dhcp NAK after interface refresh

[sgraham]

My environment has 100 or so windows clients logging into a openvpn 2.1 server that bridges to an internal network. Clinets are configured to connect and use dhcp and server is configured to issue via client connect script reserved ip addresses. Everything works fine for the most part however things get very flaky in when we take down the network interface on the client and bring it back up via code (Like when you install wireshark). The scenario goes like this...

Discovery = works fine
offer = server offers ip
request = client requests ip
NAK = server denies the request for the ip that it just offered?

At this point on (windows 7 machines) the dhcp client goes bazerk and will consume all of a sigle core machines cpu just doing dhcp requests at an alarming rate. Windows XP machines seem to rectify the problem by them selfs. If we restart the vpn client it does fix the problem but we do not want to have to write code to continually check the status of the vpn.