I checked yesterday and today a few of my sites Google cache date. I observed that for all of them the last cache storage date from July 5. I checked then the last cache date of larger sites. The sime situation. Does it mean something? What about your websites?
I have July 4 for one site, July 6 for another. Others seem to be in the same range although I have only checked a couple of pages. Google must have done one hell of a crawl that week, or perhaps found and fixed the old cache problem. It's worth looking into further...