I believe whois record nothing to do with pagerank. Changing registar may affect your domain age though. Good content, regular update & quality inbound links - do affect your future pagerank.
Hello, Yes, the pr dropped after the update. I had two pr5 websites (one for $300 and other for $190). One of them had about 2000 yahoo backlinks and 0 google backlinks- it got PR0. The other had like 15 yahoo backlinks and 0 google backlinks- it got PR1. I did not go at a loss because I manged to sell them before the update . Lucky me . Yeah, that's that. The one that got PR1 might still have some hope but the other is good for nothing. ...
It would be odd for Google to suddenly just drop the PR because someone else bought it, as long as the content and backlinks are the same the PR should stay the same