I have this problem after I upgraded from RC3 to RC4. When I go to Admin CP > vBa Gallery > Validate New Images:
Unable to add cookies, header already sent.
Same error also on "Validate New Posts" and "Edit Categories > Mass Edit / Delete" pages.
I have this same issue on both my home PC and the new server. The old server with RC3 installed is working fine.
Prevoius posts on the "Unable to add cookies..." issue say that the problem is in the white space below the ?> tag. But unless I'm completely blind, there is no white space below that tag in the adminfunctions.php page...