Just heads up on this if your PR seems to be moving around for any given internal page.
I've noticed this occuring the past two-three weeks or so. The PR for many of the pages in my site continues to fluctuate, even in between updates. These pages have been in the index for quite some time (at least 6 months), so the "newness" isn't a factor. And they are all still in the index, too.
To give an example of what has been happening. I have hundreds of deep internal pages. Some of these pages can be accessed directly from the home page, others require two layers of links to reach. For this example, this internal page has a PR of 3. Yet, sometimes the PR shows 1 instead.
After playing around a bit I think I've figured out what has been happening. The toolbar seems to at times lose some of the information that supplies the PR scale.
My site is listed in ODP. On the home page, only, it lists the category from the Google directory on the toolbar. It doesn't list the category for any other page on my site UNLESS the pages are brand new and not in the Google index yet. When I've been seeing this fluctuating PR for particular pages, what I've noticed is that the toolbar assigns a category to the particular page. It's almost as if the Google toolbar think the page is a new page, even though it isn't.
Thus, if I reach the page using a direct link from the home page, no category is listed and the PR is correct. Yet, sometimes (but not always, though), if I go through the standard links to reach the page, the PR drops and when I reach the page the toolbar shows a category for the particular page.
Since the pages properly return in the SERPS's (with the good PR, not the bad PR!), only think I can think of is that the toolbar must be losing some tidbits of information that cause the PR to display properly for any given page.
This make sense to anyone?