Error: File permission errors detected.OpenX Cache Permissions

There’s a bug in OpenX on some installations where this error is displayed when trying to login:

After logging in, you get this warning:

Error: File permission errors detected.
These may impact the accurate delivery of your ads,
See the debug.log file for the list of files unwritable

Basically error was coming from

grep -lnR 'Error: File permission errors detected.' /public_html/openx/
Result: /public_html/openx/lib/OX/Extension/authentication/authentication.php

As you can see, that authentication.php on line #171.:

OA_Admin_UI::queueMessage('Error: File permission errors detected.
These may impact the accurate delivery of your ads,
See the debug.log file for the list of unwritable files', 'global', 'error', 0);

Here is how to fix it:
Open the flowing file authentication.php from here in this location OpenXlibOXExtensionauthentication
Add the following code to line 102.“print_r($vals[‘error’]);” to line #5, right after ‘($env == ‘PERMS’) ‘

if ($env == 'PERMS') {
print_r($vals['error']);
 // Just note that some file/folders are unwritable and that more information can be found in the debug.log
OA_Admin_UI::queueMessage('Error: File permission errors detected.
These may impact the accurate delivery of your ads,
See the debug.log file for the list of unwritable files', 'global', 'error', 0);
                }

You may need to run the maintenance script for it to go away though and or wait for it to run automatically.

/public_html/openx/plugins
/public_html/openx/www/admin/plugins
/public_html/openx/www/images

Hope you will now solve this problem