Nvidia said that an investigation had identified that "unauthorised third parties" had tried to gain access to information, including usernames, email addresses and passwords.
This marks the latest attack on high-profile online forums and databases, following recent breaches on business networking site LinkedIn, dating site eHarmony, technology website TechRadar and the Yahoo Voices service.
In a message to its forum users, Nvidia said: "We suspended operations of the NVIDIA Forums last week in response to suspicious activity and immediately began an investigation.
"We apologise that our continuing investigation is taking this long. Know that we are working around the clock to ensure that secure operations can be restored."
Nvidia said that its investigation had found that hackers had tried to gain access to various pieces of user information, including usernames, email addresses, hashed passwords with random salt value and public-facing 'About Me' profile information.
The company said that it did not store any passwords in clear text, meaning that they were encrypted should the hackers have gained access to them. It did not, however, indicate how many passwords could have been at risk.
The public-facing About Me optional profiles do include a user's title, age, birth date, gender, location, interests, email and website URL, but Nvidia noted that all of this data was already publicly accessible.
Nvidia added that it is working to restore full access to the Developer Zone "as soon as possible", and will reset all forum passwords when the system comes back online.
"We are employing additional security measures to minimize the impact of future attacks," said the firm.
"All user passwords for our forums will be reset when the system comes back online. At that time, an email with a temporary password, along with instructions on how to change it, will be sent to your registered email address.
"As a precautionary measure, we strongly recommend that you change any identical passwords that you may be using elsewhere."
No-one has claimed responsibility for the Nvidia attack, but it comes after the forums of Formspring and Android blog Phandroid were also breached by hackers.