Just for future reference, just tackled this issue too after some searching. Image uploads not working, file permission error message when logging in and debug.log working, but not showing errors.
Check the "webDir" value in your configuration file under "YourOpenX/var/yourdomainame.conf.php" file.
Typical for an upgrade to forget to update the webDir value in the config file.
Joost Gysemans got a reaction from martin.krcho in "Error: File permission errors detected" after upgrade to 3.2.4