SharePoint 2010: To open this document, your computer must be running...

Problem

When a user clicks the link for a file attachment to a list item, the user first is presented with an error regarding Word Web App:

Word Web App cannot open this document for viewing because of an unexpected error.  To view this document, open it in Microsoft Word.

The user then clicks the Open in Word button, and is presented with another error:

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.  Learn more about the requirements.

The user needs to be able to actually open the document.  The user needs to be provided the ability to open the document in the client application.

Solution

1. Two separate issues:
1. Office Web App configuration.
2. Accessing 32-bit object (Word) from 64-bit application (IE9-64)
2. Ignore the first issue.
3. Have user access the document using 32-bit IE.

References

• The Office Web App cannot open an Office document in Office if the action is triggered from a 64-bit web browser
• Version of IE 32 bit or 64 bit? - How can I tell which version I am using?

Notes

• Neither Chrome nor FF get around this issue.  Involves ActiveX.