Using up available memory

Try deactivating all plugins. If that resolves the issue, reactivate each one individually until you find the cause.

If that does not resolve the issue, try switching to the Default theme (WordPress 1.5 – 2.9.2) or the Twenty Ten theme (WordPress 3.0 and higher) to rule-out a theme-specific issue (theme functions can affect anything, including memory consumption).

Use this plugin to monitor memory usage:

http://ww.wp.xz.cn/extend/plugins/wp-system-health/

Yeah, that’s basically confirming that you’re out of memory.

If you’re seeing this error either suddenly (no specific task was done to cause the error) or frequently, try deactivating all plugins to rule-out a plugin-specific issue and try switching themes to rule-out a theme-specific issue.

Otherwise, here are four ways to increase PHP’s memory allocation:

1. If you’re using WordPress 2.9.2 or lower, try adding define('WP_MEMORY_LIMIT', '256M'); to your wp-config.php file. If you’re using WordPress 3.0 or higher, WordPress automatically does this for a variety of tasks, so there’s really no reason to try it in this case.

2. If you can edit or override the system php.ini file, increase the memory limit. For example, memory_limit = 256M

3. If you cannot edit or override the system php.ini file, add php_value memory_limit 256M to your .htaccess file.

4. If neither of these work, it’s time to ask your hosting provider to temporarily increase PHP’s memory allocation on your account. Keep in mind that most decent hosting providers allocate 32 MB to PHP under each account, and most decent hosting providers allow users to temporarily increase the memory allocation. If your hosting provider won’t accommodate you, perhaps it’s time to find a new hosting provider.