That's odd? The Autocad version is not involved in this, what platform do you run on? Vista or Windows7?
CadTools overwrites current volume report file when calculating. If there's no volume reportfile the user get's a message.
If you manually try to locate the volume report file with Explorer and delete it. Then opening the volume calculation form and pressing the volume report button without doing any calculation. Then you should get the message box telling you that it's no reportfile to show. If not there is something wrong with path's and CadTools saving files.
Please inform me on how it works.