So I am running DTC ping between 2 machines on our network and am getting the following error

++++++++++++++++++++++++++++++++++++++++++++++
     DTCping 1.9 Report for WEB2  
++++++++++++++++++++++++++++++++++++++++++++++
RPC server is ready
++++++++++++Validating Remote Computer Name++++++++++++
03-03, 13:39:45.099-->Start DTC connection test
Name Resolution:
    internal-->10.20.3.236-->internal.something
03-03, 13:39:45.114-->Start RPC test (WEB2-->internal)
Problem:fail to invoke remote RPC method
Error(0x6BA) at dtcping.cpp @303
-->RPC pinging exception
-->1722(The RPC server is unavailable.)
RPC test failed

I have also run RPC ping where I get what I beleive is the same error:

C:\Program Files\Windows Resource Kits\Tools>rpcping -s internal

Exception 1722 (0x000006BA)
Number of records is: 4
ProcessID is 5876
System Time is: 3/3/2011 2:44:12:822
Generating component is 8
Status is 1722
Detection location is 323
Flags is 0
NumberOfParameters is 0
ProcessID is 5876
System Time is: 3/3/2011 2:44:12:822
Generating component is 8
Status is 1237
Detection location is 313
Flags is 0
NumberOfParameters is 0
ProcessID is 5876
System Time is: 3/3/2011 2:44:12:822
Generating component is 8
Status is 10060
Detection location is 311
Flags is 0
NumberOfParameters is 3
Long val: 135
Pointer val: 0
Pointer val: 0
ProcessID is 5876
System Time is: 3/3/2011 2:44:12:822
Generating component is 8
Status is 10060
Detection location is 318
Flags is 0
NumberOfParameters is 0

I'm pretty sure that the exception number 1722 is the key but I can't find any info about it.

There may be a firewall with ports that need opening between the machines which I am checking with our sys admins now. But I can do a regular ping between the machines.

Other than that I am reading a lot of articles talking about OS services and components I know nothing about and am having trouble finding any info on. Can anyone shed any light on this?

FYI the machine is running Windows Server 2003 RS SP2.