Okay, just to cover some basics (it's sometimes a simple oversight):

You do realize that toggling boldface or italics on does not change existing text unless you've selected some text beforehand? The usual practice is to toggle the font change and type what you want to be bold or italicized, then toggle off.

When you click on the Bold or Italics button in the Font section of the Home option on the ribbon, is that button highlighted (active) when you open the Home "menu" again?

Could you be using a font that doesn't have a bold or italic form? (I've run across a few of these.)

Anybody else out there have an idea what could be causing this?