This error message is most commonly seen when the IP address you're using is sending too many queries to Google, or when your browser's
user-agent is not reporting correctly.
If you are in a large corporate environment which uses NAT to share a single real-world IP to the entire company, or sends all web traffic through a proxy server, you stand a much greater chance of seeing this message. In these situations, Google sees all of the corporate traffic as being from a single computer (IP Address).
If your security software likes to hide your
user-agent header can trigger this error.