Incorrect error "Boost Can not write to file-system"

The error Boost Can not write to file-system is reported in the Status page, despite Boost having created quite a bunch of files and folders, like:

/cache/.boost
/cache/normal/mysite.com/.boost
/cache/normal/mysite.com/event/1977/06/10/month/all/all/1_.html
/cache/normal/mysite.com/event/1977/06/10/month/all/all/1_.html.gz
/cache/normal/mysite.com/tracker_page=215.html
/cache/normal/mysite.com/tracker_page=215.html.gz
/cache/perm/mysite.com/files/css/css_1fbbfd7dd46e4dd89e23f51dc7410765.css_.css
/cache/perm/mysite.com/files/css/css_1fbbfd7dd46e4dd89e23f51dc7410765.css_.css.gz

...and plenty other files and folders.

The actual meesage is:

Boost Can not write to file-system
Directory /var/www/vhosts/mysite.com/httpdocs/cache/perm/mysite.com credentials - Permissions: 0775. Owner 10001. Group 2524.
Your credentials - Group ID: 2524. User ID: 10001. Current script owner: popeye.

Is the error incorrect?