Can’t renew Ip address in proxy server

Hello,
Can’t renew IP address in proxy server 2.0 with external adapter that optains IP address from DHCP. This is exactley the problem I have. I copied the description from microsoft site(Q252432). I applied the solution they have on their site, but did’t help. I have to renew the IP every 48 hours. Please let me know if you have an idea.

Router: cisco 675