DNS Configuration

We have recently started migrating our NT Domain to Windows 2000 Active Directory. Before Windows 2000 we did not run a DNS server on our internal network depending on WINS for network resolution and external DNS for Internet resolution. Our website hosting is outsourced and when we set up the AD/DNS on our internal network we selected the same domain name that is used externally for our website. Now that the AD and DNS environment has been set up we are unable to resolve the website by namefrom the internal network. If we enter the IP address it comes up immediately. Is this an inherent problem with using the same domain name for our internal network or is there a simple configuration change that will resolve this problem? Thanks.