PowerPoint: Some of your fonts cannot be saved with the presentation

Problem:

When trying to save a PowerPoint file you get a message similar to the below;

In my case I checked the presentation though out and could not find "Courier" in use

Workaround:

Replace the font listed with another font;

In PowerPoint 2003 select Format => Replace Fonts

In PowerPoint 2007/2010 on the Home tab select Replace Fonts under the Replace drop-down

Select the effected font in the top dropdown, you may notice it has a question mark icon

And select another font of you choice in the bottom drop-down

Click Replace

You selected a single-byte font to replace a double-byte font. Please select a double-byte font

In my case I then got this lovely clear message, thanks Microsoft!

I ended up playing around with the font in the bottom drop-down until I found one that worked, in my case this was "Vrinda", I am told that "Arial Unicode"" should also work if you have that.