This has been coming for a while now and as of yesterday, the old format for Google News Sitemaps files has changed. An updated Google News Help thread from Googler Inbal said the last day for the old format was yesterday, May 4th. Today, the old format will no longer work, so I do hope you publishers updated your sitemaps to be news specific.
If you have not done so already, it is not too late. You can create your news specific sitemap and submit it to Google Webmaster Tools. For more details on the format, see the News Sitemaps help section and for also check out the FAQs.
This was a six-months transition period and if this is the first you are hearing of it, I am sorry. We blogged it here a couple times and I know the Google News blog also mentioned it at least once.
Forum discussion at Google News Help.