WP-Cache

Various pages suggest installing the plugin wp-cache to improve Wordpress performance. Unfortunately this plugin has a nasty bug. It seems to strike when the number of cached and expired pages is the same; at that point everything grinds to a halt. The process runs up enormous cpu time and DH kills it. Your site will serve "500 Internal Server Error" pages, and your error logs will contain complaints about "Premature end of script headers: php5.cgi".

This is nasty for a couple of reasons. Firstly, you installed wp-cache to avoid using unreasonable amounts of resources. It's the last thing you'd suspect of causing the problem! Secondly, disabling the plugin from the WP might not immediately fix the problem. (Removing it entirely from the plugin directory seems to work though.)

Elsewhere in the wiki there are some other suggestions for caching plugins. Perhaps one of those would be a better choice.