WAC scrapes google for article urls and then scrapes content from those URLs. Google will ban your ip if you scrape too many times. There are 3 ways to avoid it :
1) Use dedicated proxies - Please do not use shared proxies as they get banned very fast. Also make sure you get username, password authenticated proxies as WAC does not support ip authenticated proxies. To import proxies in WAC xtra tab go to settings and click on import proxies. Make sure your text file has proxies one per line and are in this format - ip:port;username;password (please note two semi colons)
2) Use WAC database - On left of WAC you will see quick access. Just below it there is something called readability. Click on it and change scraping articles to WAC database. Now enter your keyword in top keyword field and hit download. It will download articles. Make sure to use broad keywords though.
3) Take a pause - Do not scrape continuously. After each scrape in WAC without proxies, wait for 10-15 minutes to start another one.
If you want help create a ticket above to ask your question.