Problem adding users

Hi,

I am using gallery on a couple of sites and it is working fine apart from the fact that I can't add users. I want to password protest some of the albums using the permissions function. But when I try to add a user I get the following:

Warning: fopen("/home/katecarb/public_html/albums/.users/userdb.dat.0", "w") - Permission denied in /home/katecarb/public_html/gallery/platform/fs_unix.php on line 53

Warning: fopen("/home/katecarb/public_html/albums/.users/1033730122:1172482652.lock", "a+") - Permission denied in /home/katecarb/public_html/gallery/platform/fs_unix.php on line 53
Error: Could not open lock file (/home/katecarb/public_html/albums/.users/1033730122:1172482652.lock)!
Warning: Cannot add header information - headers already sent by (output started at /home/katecarb/public_html/gallery/platform/fs_unix.php:53) in /home/katecarb/public_html/gallery/create_user.php on line 62

Has anyone had a similar problem? Any solutions?

Thanks,

Adrian.