Domain change brings the PR down

[saran]

We are changing the domain name from brandname.companyname.com to www.brandname.com. We implement it in some of the folders and did 301 re-direction for those folders. Some folders are still with old URL.

First week the new URLs had PR 5. Now the PR gone down to 1. Any clue for the drop in the PR..

Also there is a PR difference between www.brandname.com/folder/ and www.brandname.com/folder/index.html

Why is the difference in the PR between the two pages?

Saran

[edited by: tedster at 5:00 pm (utc) on Feb. 13, 2009]
[edit reason] de-link the example urls [/edit]

[Shaddows]

Because the are different URLs. You have a classic cannonical issue. Check out this active thread [webmasterworld.com] on one way to fix that, plus the information in Hot Topics [webmasterworld.com].