A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
This is an example of why it's a really good idea to design in the same version your client is using, by means or Bootcamp or Parallels. As Steve has mentioned, font families work differently under OS X and Windows. OS X will happily gather a group of fonts and make one big family from it, but in Windows, the family must be constructed by the foundry and always has a maximum of 4 members.
The best idea is to visit your client and find out which Neutra weights are in their most used font family. This will probably be the Roman, Italic, Bold and Bold Italic, but you should check. Then on your Mac uninstall all the other weights. Set the base font in the font theme (here's my article that tells you how: XML Hacking: Font Themes). When you're creating the presentation, set the font dropdown to the theme font and leave it. The font dropdown will read Neutra (Headings) or Neutra (Body) when it's set to the theme font. Then access the other weights by using only the Bold and Italic buttons in PowerPoint. This will work 95% of the time, but you still need to test before final delivery.
BTW, your version of PowerPoint should be up to 14.6.3. Please use Help>Check for Updates to get the most recent version.