Google cache up to date?

does the cached page always match what Google is basing its results on?

[sullen]

I've just been checking out our position in Google.

We appear to have rocketed up the charts (as it were) on some search terms which relate to pages I have recently updated. However the new page is not showing in the cache.

We have also dropped a bit for other terms, but again the page in the cache is (in most case) the old one. In fact in all Google seems to have updated its cached page on only one of 7 or so altered pages.

Google has crawled all the new pages (well, Freshbot has) - could it be using the new details but not caching the new pages? Or are the result changes down to a change in the algo or other site-wide factors?