What does RPC call failed mean when executing Documents.Open thru Word interop

We are getting error reports from our customers with a

COMException 0x800706BE The remote procedure call failed

The code generating this exception is the following one:

   Microsoft.Office.Interop.Word.Documents.Open(Object& FileName, Object& ConfirmConversions, Object& ReadOnly, Object& AddToRecentFiles, Object& PasswordDocument, Object& PasswordTemplate, Object& Revert, Object& WritePasswordDocument, Object& WritePasswordTemplate, Object& Format, Object& Encoding, Object& Visible, Object& OpenAndRepair, Object& DocumentDirection, Object& NoEncodingDialog, Object& XMLTransform)

I cannot find information anywhere about what can be the cause of this exception code and I cannot reproduce it in our computers. I can get similar exceptions doing weird things (debugging and stopping it, hanging the process, etc) to Word but not this one.

Does anyone know what can mean / be the cause of this exception?

EDIT

More information. The application is a client app running on a Windows 7 computer and the error is intermitent so looks like it is not related with the environment.