I will try... but there is another post months ago by OWG which explains it better. The basic stuff I know is that, if you want to redirect one domain to another, you should use 301 redirect, this demonstrates to search engine that you are not a spammer.
Spammers tends to use HTTP refresh, JavaScript and other stuff like that but with 301 redirect you are telling the search engine that the domain/resources has moved permanently.
Do a search for 301 redirect in this forum and see if you can find OWG post on it.
I am not sure that is what is to blame for your lost of PR at the last update but then again it could be
