VPN / PPTP problems

I am trying to set up VPN on our NT server. I have started the PPTP service on our server. I have enabled the VPN adapters on our remote clients. When dialing in the host address, I get a ‘Failed to connect’ message. Just looking for ideas on how to get past the Failed to connect error. As far as I can tell, all settings are correct on the server. We are routing through a Cisco 1605R, but it is set to allow the particular IP address through that I need.

Thanks

Jerry