The RPC server is unavailable.

First things first

1. is your current DC running DNS?
2. Does the new server have the current DS as it's DNS server?
3. Is the new server a domain member yet?

aramirezomni, thanks for the quick reply!
1.  Yes, the current DC is running DNS.  On my personal computer, I set the IP for the Primary DNS to the DC we already have up and running, with no secondary, and was able to browse the internet.  I'm assuming that's a sufficient test to ensure DNS is working properly, but is there anything else I can take a look at for that?
2.  Yes, by IP address in the TCP/IP network settings.
3.  I don't think so.  I wasn't able to join the domain with the system, as per the error mentioned in my first post.  Is there something else I need to do to make a machine a domain member?

Make the new server a domain member. Then run DCPromo you should be fine.

Here is what you do:

1. Make sure that from teh new server you can ping the IP of the current DC
2. Right click MyComputer go to the network tab and change the domain to yours
3. You should be prompted for credentials
4. Once a member of the domain run DC Promo

also if you still can't join the domain it MUST be a network problem

Run CMD

then ipconfig /all

post the results here

Your first suggestion is exactly what I've tried to do several times, but get this error:
********************************************************
The following error occurred attempted to join the domain "mydomain.local":

Windows cannot find the network path. Verify that the network path is correct and the destination computer is not busy or turned off. If Windows still cannot find the network path, contact your network administrator.
********************************************************

And here's the results from ipconfig:
********************************************************
Microsoft Windows [Version 5.2.3790]
(C) Copyright 1985-2003 Microsoft Corp.

C:\Documents and Settings\Administrator>ipconfig /all

Windows IP Configuration

   Host Name . . . . . . . . . . . . : mserver
   Primary Dns Suffix  . . . . . . . :
   Node Type . . . . . . . . . . . . : Unknown
   IP Routing Enabled. . . . . . . . : No
   WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Intel(R) PRO/1000 MT Network Connection
   Physical Address. . . . . . . . . : 00-E0-81-44-FE-4A
   DHCP Enabled. . . . . . . . . . . : No
   IP Address. . . . . . . . . . . . : 192.168.1.211
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 192.168.1.1
   DNS Servers . . . . . . . . . . . : 192.168.1.200
                                       192.168.50.21
                                       192.168.1.201
                                       192.168.50.22

Ethernet adapter Local Area Connection 2:

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Intel(R) PRO/1000 MT Network Connection #
2
   Physical Address. . . . . . . . . : 00-E0-81-44-FE-4B
   DHCP Enabled. . . . . . . . . . . : No
   IP Address. . . . . . . . . . . . : 192.168.1.212
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 192.168.1.1
   DNS Servers . . . . . . . . . . . : 192.168.1.200
                                       192.168.50.21
                                       192.168.1.201
                                       192.168.50.22

C:\Documents and Settings\Administrator>
********************************************************

Also, another interesting note is that we have a few client machines on the domain, but most are just in workgroups.  I tried adding my workstation to the domain, as it is currently in a workgroup, and I got an error the first time (XP wording of the Server 2003 error listed above), but a while later I tried it again and it worked.  The Server 2003 still is not able to become a member of the domain.  Why would becoming a member of the domain sometimes work and sometimes not work?

Forgot one thing - I can ping the server just fine, no problems there.

   Hi wthero
         *Disable any firewall services on DC
         *Disable any recently installed software which may utilize RPC ports
         *Make sure "Clients for Microsoft Networks" option is checked in properties of NIC in my network neighbourhood properties.
         *Make sure RPC service and RPC locator service are running in start>run>services.msc
         
Regards

Not completely positive that that was the solution, but it (or restarting some of the DNS-related services on the existing DC) seems to have fixed the problem.  Thanks everyone for your help!

Well, it depends what those other DNS servers were doing there to begin with. If you're only adding a second domain server then you really only should have ONE dns server internally. Every single computer, server and DC in your domain should be pointed at that one internal DNS server and then that DNS server should have external DNS servers in the forwarders. Those are all internal addresses but my concern is why the two different subnets? Do you have a domain trust relationship going with another domain? Do you have subdomains of any kind?

We set up all of our workstations to point to two different DNS servers.  One of those servers is our PDC locally, and one is our ISP's server (we have T1 internet access).  So if our main server is down for whatever reason, our employees still have access to the internet through our ISP's server.

Putting that IP in as the secondary DNS server was almost "automatic" to me because I've set up so many client workstations with both of those DNS's set.  I didn't think about any consequences it might have on the ability to set up the new server as another DC.