Cannot open the file: mk:@msitstore

When I compile an HTML help file with Adobe RoboHelp, a [.CHM] file is generated. I have done this thousands of times. My CHM is then sent to a programmer who includes it with a software program.

No changes have been made to my project, but my compiled CHM is not opening! This is a huge problem. When I double-click on the CHM, I get a dialog with the message "Cannot Open the File: mk:@MSITStore".

What does this mean? How do I correct the problem?

http://www.smartcomputing.com/TECHSUPPORT/detail.aspx?guid=&ErrorID=25904
This error can be caused by a program installation or the un-installation of a program that for whatever reason un-registers the hhctrl.ocx file. To fix this error, you will need to re-register the hhctrl.ocx file with Windows. Click on your Start menu and select Run. In the Open portion of the dialogue box that appears, type regsvr32 %systemroot%\system32\hhctrl.ocx. Click OK and the error should be fixed.