Checking the presentation, this font didn't seem to be used anywhere -- I even went as far as to click on all the text in the file (which showed up as either Arial or Helvetica). Attempting to use Format: Replace Font would only allow the Asian double-byte font to be replaced with another double-byte font, which caused the same error. Naturally, nowhere in the process does PowerPoint make it clear where the font is theoretically being used. Under normal situations, it would be safe to ignore the ghost font, but that wasn't the case here.
So, what I did was:
- Save the PowerPoint file as a web page, which causes it to spit out a slew of CSS, XML and HMTL files.
- Opened all the htm files in TextWrangler (or the html editor of your choice which allows multi-file searches.
- Searched for the font by name.
I imagine this technique would also work in any Office application, and probably on any platform.

