mailto not splitting cc & subject

Not really VBA, but I have a Word document with mailto hyperlinks to start an Outlook message. Something like this:

mailto:[email protected][email protected]

The hyperlinks have always worked fine, but now it doesn't work for one person who was having email problems and apparently had Outlook reinstalled (or something). Now on that one PC, clicking the hyperlinks opens an Outlook email but puts the whole line in the To field. So the To field looks like "[email protected][email protected]" and there is nothing in the Cc field (or Subject field for URLs that have subject=). Works fine for everyone else (same versions of Word and Outlook). Any ideas?