OMG, that happened to me all the time when I was pregnant! Any time I got the slightest bit cold, my nipples turned white or purple and hurt like heck. After I gave birth, it never happened again. I never knew what it was, so thanks for posting that article. The article seems to have some good tips for making the pain go away. Good luck and hopefully it's just temporary for you too.
Proud Mama of M (11/6/06), wife to T (7/31/04) and teacher of 23 first graders