[SOS!!!] What happened to my site ranking? Drop from 5 to 0!!!?

[Bay]

I've read the FAQs and searched the help center.
My URL is: http://www.bayvoice.net

Hello,

We optimized our website structure, changing article
http://www.bayvoice.net/newbv/article.html
to:
http://www.bayvoice.net/gb/article.html

Our mainpage changes from http://www.bayvoice.net/gb accordingly.

For all the articles,we have done 301 redirect.

BUT, I still found our page rank drops from 5 to 0 !!!!

And, there are lots of articles who have very good keyword position in google search results, now they just disappears in google search page.

Anyone can tell me what should I do?????

Thanks!
Bayvoice