Is it possible that google is updating in a new way -
add the PR and backlinks....but the SERPS aren't changing. They may not change the SERPS until they've applied filters and such. Why else would there be some big changes in the backlinks for lots of sites and PR additions on sites that are only a couple weeks old in some cases, yet the SERPS don't have any significant movement. Maybe the dance is broken up into songs now.
Dunn