Commented Unassigned: 0x800700C1 Error Message [8803]

The properties are shown at the bottom of the explorer page, but after I type a new value in a field, like Title, when I select save, I get an error message:
Error 0x800700C1: MyFileName is not a valid Win32 application.
I am running 64 bit Windows 7 and the file is a pdf.
Comments: ** Comment from web user: klembeck **

I tried to reply to your email, but got a failed delivery message, so here is what I sent:

Sorry about the bitmap. However, it was just a shot of the error message which I already quoted.

The registry key for the .pdf is {D06391EE-2FEB-419B-9667-AD160D0849F3}

I was not able to attempt to edit .txt fields, so I activated the .txt editing via your tool, and now I see fields to edit, but when I click Save, I get the same error message as for the .pdf.

I am able to edit .docx and .jpg fields. I have not selected them in your tool.

When I try .log files, get error 0x80004005:Unspecified error. I have not selected .log in your tool either.

By the way, I have rebooted and still get the errors.