MS Word 2010. I have a strange formatting problem.

I must have changed a paragraph or style setting, perhaps by mistake.

Whenever I try to apply a style to one specific character (bold, for ex.), the style applies not only to that character but also the two characters AFTER it.

If I bold the last character of a word, then the first character of the NEXT word then bolds. Sometimes it happens in the word PREVIOUS to my character selection.

I have never seen this before in 12 years of MS Word usage. What did I do?