[Plugin: WP Super Cache] Cache directory not writeable

I have been trying to get the WP Supercache Plugin working, but could not get past an issue with directory permissions.

Here’s the error I’m receiving:
Error: Your cache directory or 1 need to be writable for this plugin to work. Double-check it. Cannot continue… fix previous problems and retry.

I’ve tried relaxing access controls and experimenting with different ownership of the indicated directories: chown, chgrp, chmod 777 on wp-content and wp-content/cache

Any ideas as to how to get around this error? Thank you very much for whatever help you can provide.