I'm having problems with my ASP.NET web forms system.

It worked on our test server but now we are putting it live one of the servers is within a DMZ and the SQL server is outside of that (on our network still though - although a different subnet)

I have open up the firewall completely between these two boxes to see if that was the issue and it still gives the error message "Communication with the underlying transaction manager has failed" whenever we try and use the "TransactionScope". We can access the data for retrieval it's just transactions that break it.

We have also used msdtc ping to test the connection and with the amendments on the firewall that pings successfully, but the same error occurs!

How do i resolve this error?

Any help would be great as we have a system to go live today. Panic :)

Edit: I have created a more straightforward test page with a transaction as below and this works fine. Could a nested transaction cause this kind of error and if so why would this only cause an issue when using a live box in a dmz with a firewall?

AuditRepository auditRepository = new AuditRepository();

            try
            {
                using (TransactionScope scope = new TransactionScope())
                {
                    auditRepository.Add(DateTime.Now, 1, "TEST-TRANSACTIONS#1", 1);
                    auditRepository.Save();
                    auditRepository.Add(DateTime.Now, 1, "TEST-TRANSACTIONS#2", 1);
                    auditRepository.Save();

                    scope.Complete();
                }
            }
            catch (Exception ex)
            {
                Response.Write("Test Error For Transaction: " + ex.Message + "<br />" + ex.StackTrace);
            }