NVIDIA have just announced they've "suspended operations" of the NVIDIA Forums, for what seems like a breach of their systems. They've run a preliminary investigation, where they've identified that unauthorized third-parties gained access to some user information including usernames, e-mail addresses, hashed passwords, and public-facing "About Me" profile information.
NVIDIA state that they didn't store any passwords in clear text, and that their "About Me" optional profiles could include a user's title, age, birthdate, gender, location, interests, e-mail, and website URL, all of which was publicly accessible. NVIDIA also add that they're continuing their investigation, and hope to restore the Forums soon. They're also implementing additional security measures in order to minimize the impact of future attacks.
All passwords will be reset when the Forums go live again, and at that time NVIDIA will send out an e-mail with a temporary password, as well as instructions on how to change the password. NVIDIA (as well TweakTown) recommend that if you have any identical passwords on any other site, that you change them as soon as possible.