I am developing drupal sites locally on my MacBook using MAMP.

I was getting a lot of memory limit errors.

I modified the php.ini file and also the settings.php fiel in drupal. None of them solved my problems.

I inserted this line in my .htaccess file inside the drupal folder:

php_value memory_limit  "100M"

That line goes right after

# PHP 5, Apache 1 and 2.
<IfModule mod_php5.c>

This solved my problem.