Cannot select a font style in the textfield properties panel

When I select a text field on the stage to edit its properties (font family, style etc.), the drop down box to set the font style is disabled/greyed-out. Any font I select, it's just not possible for me to set a style for it.

It's the same in the font embedding window; I select a font, but cannot select a style.

Now, I've asked my colleagues to see if they have the same problem. But it's all fine on their installations.

So i'm at a loss as to what's going on. I've uninstalled and reinstalled, cleared my font cache...

I hoping someone can shed some light on this issue, or point out where I'm going wrong!

System:

OS X 10.9

Flash Professional CC 13.1.0.226

If anyone needs more info about my system, just let me know what you need and I'll provide it.

Thanks in advance.