Adsense DOWn - Why are links taken down?

Why is Google removing links?

[xenithforever]

We have a number of Directory Generator created pages.
About 1/4 of them have been upgraded to have rotating articles
on all the pages. Until just recently, most of them had either
a PR2 or PR3. Now, several of them... in fact, some of the most
productive of them, have gone to PR0... and have dropped out of Google.

As a result, our revenue has really dropped:

Any answers appreciated.

Dave

[europeforvisitors]

Have you tried the Google News forum?

For what it's worth, in the last month or so I've seen a greyed-out toolbar on some Forbes.com pages that were PR6 for months, so it's possible that either the toolbar is wrong or PageRank calculations have been goofy in recent weeks. (Somehow I doubt that Forbes is in trouble with Google.)