500 error on some page loads

Hi all!

I am having a problem with a website right no. Once in a while (every 5 page load), I will get a 500 error. PHP error log file states this:

[04-Jan-2012 21:37:28] PHP Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 77 bytes) in XXXXXXXXXXXXXXXXXXXX/wp-includes/pomo/mo.php on line 219

Host is Laughing Squid.

How can I make sure this does not happen?

Thanks for your help!