tedster - 5:49 am on Jun 7, 2010 (gmt 0)
It's not totally new - although this particular method of reporting may be. I never let my sites return a soft 404 - it's one of the first things I check - so I won't see this kind of report.
A "soft 404" means a page that has content that seems to be a 404 error message, but the page itself is being sent with a "200 OK" HTTP status. Some IIS servers, in particular, are configured to serve custom error pages this way, usually with a 302 Temporary redirect from the requested URL.
It is a technical error, because the 404 Not Found status never gets sent to the requesting user agent - googlebot in this case.
A few years back, this situation caused some sites to pile up a huge amount of duplicate content over time, because every "bad" URL request or link would be indexed with the text of the error message. A 302 redirect normally means the original URL is indexed, but with the text of the redirect target. Then Google began actively testing servers for their 404 handling, especially IIS servers. They don't want to pile up that kind of data in their index.