Word 2007 character spacing with Em dash

My coworker is experiencing weirdness with some Word body text styles. When
an em dash is included in a sentence with one of these body text styles
applied, the dash is literally shoved on top of the left and right
neighboring letters. It resembles strikethough. When the style of the
sentence is changed to Normal, the problem goes away.

I've inspected the style which is still defined as it was designed and a
pretty standard style (10 pt Arial, left aligned, 12 pt exact line spacing).
There is no character treatment applied to the font.

Has anyone else ever encountered anything this and know what the fix is?