There is a good chance you know this already but the default memory setting for PHP on the server is too small to run a Drupal site that has multiple modules.
When this site was D4.6.8, I had to increase the memory setting for PHP on the server. Fortunately, my service provided allows for this. I assume it is because I have a virtual server at Prohosters/Carpathia. When I upgraded to D6, I had to increase my PHP memory. We bumped it up to 32MG to give me enough wiggle room. I have the option of going to 64MG but decided to wait.
PHP upgrade process
I just updated to PHP5.2. You may recall I delayed updating until I had my old D4 site on another server before breaking it with an update to PHP5.2. Anyway, we just did the update over night and apparently, the process reset the PHP memory back to its default. I awoke to a fatal error, not enough memory. My provider set it back to 32MG immediately upon advising them of the situation.
So, when updating to PHP5.2, two things to watch out for:
- Make sure that all applications on your server using PHP can operate with the version you are going to.
- Make sure that the memory setting isn't reset to default when you need more.