I've had my 2006 Prius since Jan. Today it started giving me a warning when I put it into drive. The warning was the battery coudn't charge while it was in neutral. It told me to place it in park. I did. I repeatedly tried and even drove out of my parking but it continued to say this with the ! in the triangle appearing. I've never even put it in neutral before. Any thoughts?
The warning that you got is one of the random precursors of your 12V battery dying. Typical 12V battery service life is ~4 years. It is time to get a new one... tomorrow wouldn't be too soon.