Both scrapers have limits on the # of requests you're allowed to make. TheGamesDB has a monthly quota of about 15000 requests (not sure), while ScreenScraper will give you I think 10000 requests daily. If you exhausted your request limit, you'll not be able to scrape - you'll have to wait.

EDIT: seems like ScreenScraper has a few problems at the moment and scraping from it will not work until they sort out the issue.

@bfollowell It's possible that the data you had already scraped was cached on your computer and that was why previously successful scrapes still appeared to scrape correctly and new scrapes did not.