I wanted to post this discussion to stick to the very specific topic of internal page rank fluctuation and actual first hand knowledge of it happening to your site or one you have seen.
I have a site which has EXCELLENT ranking for huge money terms and has for the better part of two and a half years now and still does. About a year and a half ago I read Brett's successful site in 12 months on google and after reading realized then content was going to be a lot more important to google in the future hopefully so I created about 50 pages at the time for this one site. My home page is now a pr 7 and all internal pages go down one point for each deep level you go down.
Yesterday, I noticed that one of these pages on the 3rd level deep in my site went from a pr5 to a zero....I have 5 other pages crosslinked with that one page and have for a year and a half and they still had pr 5's...I thought it was odd being as my home page and all of my other internal pages were still the same pr but maybe a hiccup? This morning I check the same page and still a pr zero only now the 5 other internal pages that I link to from the now pr zero page have went from pr 5's and 6's to pr 1's and 2's....I do not understand why pages that have had good pr for the better part of a year and a half with no changes whatsoever lose pr when the homepage has not and the ranking of these pages has not changed either...the pr zero page is still ranked no. 4 out of over 300,000 results. And another odd thing is just a while ago for about a minute these pages were at thier original pr of 5 or 6 and then went back down again. How strange.
Have any of you seen similar behaviour? Could this be a hiccup? And, if in fact the pages have been penalized will this end up affecting my homepage and spreading like a cancer through my site?