There is a good article on this subject here: Troubleshooting Problems with MSDTC. It was originally written for BizTalk Server but applies on other server as well.

Since you're running off a VPC, it's possible the DTC shares some identifiers with another machine on the same network. Please check the "Ensure that MSDTC is assigned a unique CID value" chapter in this article (see also http://blogs.msdn.com/b/johnlee/archive/2008/09/09/msdtc-on-virtual-machines.aspx), although I believe DTCPing should tell you about it... You can also try msdtc -uninstall and msdtc -install to fix this.

You should also check if your server are not using some VPN or encryption technology. I kinda remember this can cause issues.