Problems with Office 2008

Hi, I just upgraded from office 2004 to office 2008. However, there something that bothers me with 2008..

in 2008, I used to be able to open different document in different spaces (I have Leopard).

However, I cannot do that anymore in 2008. Whenever I open a document in a new space, the previous document will also be drag into the same space automatically.

Is there anyway (change setting?) to fix this problem?

thanks