This is a strange situation I've run into and I was just curious about your thoughts on this. I have a site which after the recent PR Update, 2 of it's pages increased their PR even though each lost backlinks. Does anyone know why something like this would happen?
If you are linking to the pages from your home page and the home page has gained PR, this may flow to the other pages on your site. So while you may have less backlinks, if the pages linking to these pages have increased their PR, this will flow to these two pages, thus pushing up their Pagerank.
It's really difficult to tell, especially without seeing the site. If we don't know the website it's just a guessing game and my best guess is that pages linking to that page have increased their own PR. On site factors may also come into play - your nagivation structure for example and the content of those two pages.