PPT 2003's exports top out at around 3000+ pixels.
If your slides are about 10" wide, no problem; but you won't get 300dpi at
anything higher than that.
Some versions of PPT spit bad TIFFs intermittently for no apparent reason.
If you run into trouble with apps that won't read your TIFFs, have PPT make
PNGs instead. Convert them to TIFFs in some other app.