Directory permissions for CKFinder/image uploads? [SOLVED]

[artfulrobot.com]

The Browse Server (for images to insert into a mailing) button has stopped working recently - says it can't access or create the thumbnails directory.

I'm sure this is a Unix permissions thing but I've set all the obvious ones and I'm stuck as to which folder(s) it needs access to. Can anyone help?

I'm on Drupal 7, Civi 4.3.5. The following dirs are writeable by the user that the webserver runs as

• sites/default/files/civicrm
• sites/all/modules/civicrm/packages/kcfinder/upload

[artfulrobot.com]

I'm not sure how it happened, but in case anyone else finds this post looking for the answer...

It saves to
./sites/default/files/civicrm/persist/contribute/images
and makes thumbnails in
./sites/default/files/civicrm/persist/contribute/.thumbs/images

I think perhaps the hidden .thumbs folder was wrong - and I hadn't seen it because it's hidden.

All good now.