Cant access my web address from inside the office LAN

Let me give a little background information on our office setup:
- Watchguard SOHO 6 Firebox, Router Firewall that controls the DHCP
- Compaq ML350 Proliant Server running Windows 2000 Small Business Server, with Active Directory

The gentleman who originally setup this box I believe did not setup the domain properly. Currently, we have one of our many domain names via Network Solutions pointing to our sole IP number going into the office, and our actual domain that users log onto is for this sake COMPANYNAME, and on the domain controller is named COMPANYNAMETECH.local. I can access a computer running IIS by typing into IE pc.companyname.local and it comes up, but if I try the domain name www.companyname.net internally, it wont work. I even have on the firewall port 80 pointing to the server running IIS. I do not want to use the simple workaround of changing the HOST file to 10.1.2.4 www.companyname.net, since the majority of the PC's on my network are laptops and are mobile 50% of the time. I feel that the problem is in the firewall, but not totally sure, Watchguard is a pain in the rear to talk to since most of there techsupport group are foreign. And if you want a American tech support, the have to call you back, and they never do.. Please help, we are launching a web app in a couple weeks that needs to be 100% accessible inside and outside the network without making any changes to the settings on the laptops.
Thanks in advance,
Bryan

If you try to ping www.companyname.net when internal, do you get a public IP address or is it returning a 10.1.2.x address? If you're getting a public address back, then that may be part of the problem, since the box that is doing the DNS resolution is assuming that the requests are coming from outside, as opposed to inside the network.

We had the same type issue here and we solved it by creating a separate forward lookup zone in DNS for connecting internally. Example:

external users would connect using: www.testname.com
internal would use: newtestname.com

that way, the external users will see it the same way they always have, and internal users can still get to it without host entries, etc. granted we have to remind people about leaving off the www part internally at times, but it seems to work pretty well.

There's probably a better way, but since no one else has responded, I figured I'd give it a shot...