I once had a friend's page (3 mths ago) that was indexed, and it is still in google's cache and being indexed.
That page has nothing but a logo. Now that the page is updated, google still shows the old page.
Sometimes I just don't understand google.
Making a long story short, Google is broken. Longer explanation is that Google crawls sites with high PR and high TrustRank, so Google tends to have the latest pages in those sites cached, but Google barely crawls sites with low PR and low TrustRank, and thus, this creates various problems as far as users are concerned.