pureftpd no longer works after upgrade to 4.4

I have upgraded a couple of WordPress sites on my development server to 4.4. In both cases I am no longer able to update any plugins or themes, etc. Instead I receive an error message that WordPress is unable to create the folder.

I have double checked permissions (which are all set to 777 on the dev box) and have also double checked some 4.3.1 sites which all work fine.