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Hey, you have pretty much answered this question yourself - "we suddenly dropped to a PR1 but our traffic wasn't seriously affected". If this is the case, then, I would not worry about the toolbar page rank. Also, you have a raft of other problems, but you seem to have a handle on those. I would spend your time constructively focusing on getting your new site up and running and resolving all these duplication issues and not spend another minute worrying about your loss of page rank.