I have no idea where the bug is, I know these three mods are installed in both the forums I've see it.
8: Undefined index: actual_theme_dir
File: /Sources/Load.php
Line: 2447
That correspond to:
// Default language directories to try.
$language_directories = array(
$settings['default_theme_dir'] . '/languages',
$settings['actual_theme_dir'] . '/languages',
);
in getLanguages.
What drives me crazy is that it happens from time to time, and I have never been able to reproduce it reliably.
Last time I tried to reproduce it it was kind of associated to the use of language=something in the URL, but apparently not is not, so... ohh I have no idea, just posting here so that if anyone has an idea he can post.