Uh Oh... I Tried Disabling The Cache And Admin/Modules stopped working

I read a support post here which said that to properly disable all caching add the following lines to settings.php.

if (!class_exists('DrupalFakeCache')) {
  $conf['cache_backends'][] = 'includes/cache-install.inc';
}
// Default to throwing away cache data
$conf['cache_default_class'] = 'DrupalFakeCache';

// Rely on the DB cache for form caching - otherwise forms fail.
$conf['cache_class_cache_form'] = 'DrupalDatabaseCache';   

I had to change the permissions to settings.php from 505 to be able to overwrite it.

Well... it seemed to work. But then I decided to turn caching back on (by replacing the file with the original version). And now the Admin/Modules page is blank. Other functions work OK.

Any ideas on what I did wrong...and what to do about it? I can't be the first moron to have slipped up like this.

TIA,

---JC