Mac Student drop box folder in Server 2003

I have a Windows Server 2003 R2 SP2 as a file server.

The students are using a Mac Pro OS X 10.6.8 computer.

The students are using a domain user called Students.

Here is my folder structure:

Root Folder

Group A (shared as group a)

Here are the student's security permissions on the folder group A (they have full control on the share permission)

On a windows computer, I can map a drive there and copy files perfectly (just like how a drop box should work)

On the Macs, I'm able to connect to the folder (via connect to server) but I can't copy and files into the folder.

I get this error code -36 saying "The Finder can't complete the operation because some data in "Filename" can't be read or written."

I'm not too sure if this is the right forum to put it in but can anyone help me out?

Thanks,

D