g1smd - 8:04 am on Apr 27, 2010 (gmt 0)

I'm also seeing recently changed pages appearing in SERPs for keywords that do not appear in the cached version, not sure if that's related.

This is serving results from the Supplemental index. Google keeps old copies of pages going back months, maybe as long as two years, and the URLs will continue to appear in SERPs for any words currently or previously on those pages, whether or not those words are still on the page now. This has been normal Google behaviour for many years. I noticed it after updating some contact details on a site. All the pages were re-cached and re-indexed and appeared in searches for the new details, however, even six months later searching for the old details still brought up the URLs for these pages in SERPs even though the old details were not on the real page nor in the visible Google cache. In fact, in the cache view the terms were highlighted as "the following terms only appear in links to this page" which isn't really the right message because the terms don't appear anywhere on the live web and certainly weren't in any anchor text pointing at those pages.