I had a report today of someone who couldn’t open a Word document that was part of their Agenda list in a Meeting Workspace area. They would click the clink and the document would open in the browser with Office Web Apps, but then it would fail when trying to open in Word. The error message was as follows:
Microsoft Word Web App
To open this document, your computer must be running a version of Microsoft Word and a browser that supports opening files directly from the Office Web Apps.
Some research turned up this KB entry from Microsoft:
In this case, Office 2007 had been uninstalled, but Visio 2007 was still floating around. They uninstalled Visio 2007 and Office 2010 to make sure everything was cleaned out, and then reinstalled Office 2010. Once that was done, everything opened perfectly.