A font in some PPT is not present on a machine. Windows and Office have to substitute a font.
http://www.google.com/search?hl=en&source=hp&q=Change+the+default+font+in+Powerpoint+2007 covers how to change the default font.
http://support.microsoft.com/kb/826832 should be reviewed since you may want to EMBED FONTS into your Powerpoint files so they display on other machines with the intended font.
Bob
I have Vista and Office 2007. I work on Powerpoint Presentations. Lately I find that several of the fonts I'm using are defaulting to Arial. This is the case particularly for fonts beginning with an A, for some reason (Architect, Aquaduct, Aramis...) Then yesterday, suddenly it all defaulted to what looked like Architect! I should point out that the font I'm using shows in the font selection box but it defaults to something else on the slide.
I appreciate any light you can shed on this. Unfortunately I don't understand fonts that well (truetype, etc). -Rain

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