Hierarchal folder permissions problems MacOS Snow Leopard and Lion: permissions set for a folder aren't inherited by new files copied into it or created in it.
This is actually the correct mode of operation for your OS. This improves the security of the operating system by ensuring that all expanded permissions must be intentionally set, rather than simply inherited. However, you can change this by using Access Control Lists (ACLs) in OS X.

Using the Terminal app in Application > Utilities, navigate to the parent folder in question using the cd command. Then, run the following commands:

chmod -R 774
chmod +a "group file_inherit,directory_inherit" .


The first commands allow everyone in the folder's user and group to access all files and folders in the directory, and allows people outside the group to read the files. The second sets those permissions to inherit  to all new files and folders within the shared directory.

For more information on chmod syntax and man page, look here:
http://ss64.com/osx/chmod.html

And here is a general chmod tutorial:
http://catcode.com/teachmod/