No, it won't have an adverse affect on carear prospects, I've been doing it for three years. If anything its helped me land some great internships/jobs becuase I have time to network and work PT during the day. I was FT and switched to PT, for me smartest thing I ever did.
If anything, I think going PT can help job prospects. My experience is that nobody holds PT status against you, but your job experience can only work for you.