QuickCache not working, permission issues

Although it does appear to be working, we’re getting constant permission error messages from QuickCache.

Any time you open QuicCache Options, it says:

Permissions: Please check permissions on /wp-content. Quick Cache needs write-access to this directory. Permissions need to be 755 or higher.

When you save settings, it says

Error: Could NOT enable Quick Cache. Please check permissions on /wp-config.php, /wp-content/ and /wp-content/cache/. Permissions need to be 755 or higher.

Permissions: Please check permissions on /wp-content. Quick Cache needs write-access to this directory. Permissions need to be 755 or higher.

WP-config permissions are currently set to 666, we’ve tried 755, but that makes no difference
wp-content permissions are set to 755

Again, caching appears to be working, cache is created and cached versions of the pages are served.

I’ve searched the forums, there seems to be a lot of complaining about this, but no real solutions.

Would appreciate any pointers how to get this to work properly.

Thanks