If you have experienced any issues with twitter integration in Windows Phone Mango, Microsoft just posted an update on the issue,
we experienced a hiccup in our Twitter connection for contacts, but the connection is up and running again. Your contacts will reappear in the next 24 hours. Your Twitter feed and ability to post to Twitter remain otherwise unaffected. You may need to re-pin Twitter contacts to Start, re-add Twitter contacts to groups and re-link any Twitter contact links done manually. Sorry for the inconvenience.
Good to see faster response from Microsoft.
via: Joe Belfiore