Hey, my gallery has always worked fine until recently. Whenever I try to FTP some files over and then batch add them I get to the screen where you tick the pictures and select an album but the message "Warning: the script can't write in this directory, you need to change its mode to 755 or 777 before trying to add the files !" appears at the top of the page.
I won't pretend to know exactly what this means, I have read through the troubleshoots and checked my permissions and can't see the problem.
I'd really appreciate some help, thanks a lot.
Don't check permissions, but set them. Read the permissions section (http://coppermine-gallery.net/demo/cpg14x/docs/index.htm#permissions) of the docs extra-carefully.
My permissions are all set correctly but I'm still getting the error message
How do you know that they are set correctly? Did you actually read the entire permissions section of the docs? Unless you're the server admin, you can't know for sure what permissions are actually needed. Although 777 works for most, for some it won't work, depending on the server setup. This isn't something that we (coppermine supporters) can solve for you. As suggested in the docs, you'll have to contact your webhost for support if you can't fix permission issues on your own. They may have to change ownership for you as well (CHOWN).