I was happily coding a solution for common problem of writing data in a distributed transaction fashion.   This was the first time I encountered the latest in security changes with service packs on workstation and server and the MSDTC.   Most of the information is available in Microsoft KnoledgeBase but I found a couple more symptoms that may be of interest.

Please note that the following information may help resolve the problems found, however it introduces potential significant vulnerabilities and appropriate security measures should be taken and the items below adjusted to properly enforce security in a production or similar environment.

• MSDTC on server 'ClientComputer' is unavailable
• OLE DB provider "SQLNCLI" for linked server "RemoteServer" returned message "No transaction is active."
• New transaction cannot enlist in specified transaction coordinator
• Error 8004d00a. Distributed Transaction error
• The operation could not be performed because OLE DB provider "SQLNCLI" for linked server "RemoteServer" was unable to begin a distributed transaction
• Server: Msg 7391, Level 16, State 1, Line 1 The operation could not be performed because the OLE DB provider 'SQLOLEDB' was unable to start a distributed transaction.

1. Make sure MSDTC running on both machines
2. Follow instructions found http://support.microsoft.com/?kbid=873160
3. Although I did not have to reboot, some individuals on the internet required reboot to get the MSDTC settings to take affect

How to troubleshoot MS DTC firewall issues
http://support.microsoft.com/default.aspx?scid=kb;en-us;306843

DTCPing troubleshooting tool
http://support.microsoft.com/default.aspx?scid=kb;en-us;306843

Original article that helped the most with configuration of MSDTC
http://support.microsoft.com/?kbid=873160

Vulnerabilities in MSDTC and COM+ Could Allow Remote Code Execution (902400)
http://www.microsoft.com/technet/security/Bulletin/MS05-051.mspx