Error Message When Transferring Certain Files from One Mac to Another

I am trying to transfer files from my iMac to my MacBook Air (I am set up for read/write permissions on both computers), but I get the following message when trying to transfer to the "Public" folder:

"The operation can’t be completed because you don’t have permission to modify some items"

The files in question are not locked. Some photos transfer, some do not.

Both computers are using Mac OS X V 10.6.5