Recently we worked with a client who upgraded their Office to 2013 and ran into this error with editing a template in ACT. The full error was:
"Unable to cast COM object of type 'Microsoft.Office.Interop.Word.ApplicationClass' to interface type 'Microsoft.Office.Interop.Word._Application'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{00020970-0000-0000-C000-000000000046}' failed due to the following error: The RPC server is unavailable. (Exception from HRESULT: 0x800706BA)."
This post shows the workaround.
The following are registry keys you will need to modify. The registry key is LoadBehavior. It needs to have its value changed from 3 to 9. It can be found in the following locations:
For 32-Bit Version of Windows HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Word\Addins\ACT7.OfficeAddIn HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\Word\Addins\ActOffice2007Addin.Connect HKEY_CURRENT_USER\Software\Microsoft\Office\Word\Addins\ACT7.OfficeAddIn HKEY_CURRENT_USER\Software\Microsoft\Office\Word\Addins\ActOffice2007Addin.Connect For 64-Bit Version of Windows HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\Word\Addins\ACT7.OfficeAddIn HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\Word\Addins\ActOffice2007Addin.Connect HKEY_CURRENT_USER\Software\Microsoft\Office\Word\Addins\ACT7.OfficeAddIn HKEY_CURRENT_USER\Software\Microsoft\Office\Word\Addins\ActOffice2007Addin.Connect
The source for this fix is from the ACT knowledgebase: article 36939.