WinHelp to HTML conversion problem.

I am converting a WinHelp project to HTML Help and have elected to import my .HPJ file to an HTML project. All seems to go well with the import. When I open the project from RoboHelp HTML, I can generate HTML help "successfully" but when I try to open the CHM file, I get this message: "Cannot open the file: mk:@MSITStore:D:\... ...\!SSL!\Microsoft_HTML_Help\MyProject.chm"

I have successfully converted several other WinHelp projects with this approach.

My coworker tried the conversion on a different PC and experienced the same problem.

Any suggestions?