Hi MCF and welcome to the RH community.
The first thing I'd do is install a version of Word that is supported by RoboHelp X5 . Even the 5.0.2 patch only supports use of MS Word up to 2003. Office 2007 is only supported by later versions of Robohelp. So the other option is upgrade your RoboHelp licences to the latest RoboHelp 8 vsersion.
Read the RoboColum(n).
If what Colum offered isn't making sense it may be because you may be referring to links you have created from your RoboHelp topics to Word documents.
Is this the case?
If so, are the documents existing in the list of Baggage Files?
Helpful and Handy Links