Troubleshooting Google Buzz - Error 502

You might see a Temporary Error (502) when you try to log in or use Gmail and/or Buzz. This error, while rare, still does occur. Error 502 is Google’s way of saying that Gmail and/or Buzz is temporarily unavailable at the present time. Google and/or Buzz might be unavailable for a number of reasons, such as its being upgrading to a new version. Google generally provides more detail when Gmail or Buzz is unavailable. The cure: Wait for Gmail and/or Buzz to return—502 errors usually last only a few minutes. If you keep seeing Error 502 over some length of time (for an hour or more), try clearing your browser’s cache (browsers sometimes retain a page in memory and keep showing you that page over and over when you try to access a site).

Source of Information :  Pearson-Sams Teach Yourself Google Buzz in 10 Minutes 2010