To add to Colum's remark:
I noticed this in TFS and VSS, so I suspect the same goes for SVN: The problem here is that RoboHelp doesn't support moving files in version control. When you move a file, RoboHelp will delete the existing file and will add the file in the new location as a new file in the version control. So the problem here seems to be with RoboHelp instead of SVN.
Kind regards,
Willam