Users in both Australia and the US reported that entering Web search queries produced the response "Your search did not match any documents", even when the search term would normally be expected to produce a large number of results.
Experimenting by ZDNet Australia and user posts suggested that the problem was occurring intermittently, rather than for users of a particular browser or ISP. It did not appear to affect Google's specialised searches for images, news or newsgroup postings.
Forum posters theorised that a virus could be responsible, although the fact that Google continued to deliver relevant advertisements linked to the search terms suggests that is unlikely to be a local PC problem.
Google Australia representatives did not immediately return calls seeking comment.