Can you tell if this FAS2040 participating in the Windows 2008R2 domain as well ? Are these the trusting domains ? What about the username that you are using to manage the filer using Computer Management, is that part of the filer's local administrators group ?
One other thing to keep in mind, in Windows 2008R2, you don't need to right click "My Computer" and click "manage", rather you need to go to the Admin Tools and select "Computer Management" from there to connect to the filer.
-Reena
