This was a first. I logged into one blog's WordPress Administration panel and rather than seeing the Google Analytics summary, recent drafts and other widgets on the Dashboard, I saw this error message in their places:

Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 30566 bytes) in /home/public_html/wp-includes/http.php on line 1033

Fortunately the problem wasn't really ‘fatal' (in the usual meaning of the word) and required a very simple fix.

Just edit the wp-config.php file to include the line below:

define(’WP_MEMORY_LIMIT’, ‘64M’);

You can do the same thing by changing the line in your wp-settings.php file from:

if ( !defined(‘WP_MEMORY_LIMIT') )
define(‘WP_MEMORY_LIMIT', '32M');

to

if ( !defined(‘WP_MEMORY_LIMIT') )
define(‘WP_MEMORY_LIMIT', '64M');

but the problem will be back the next time you upgrade WordPress, so changing the wp-config.php file is preferable.