If you have not updated in a while you may want to have a look at your templates and upgrade your installs. If you read the linked article don’t skip the comments.
This is another of many reasons why this site has remained on MovableType.
On a couple of my wordpress installs on other domains I have been negligent in updating the installs and have had issues in the past. It’s to bad that wordpress users continue to suffer from security holes in older versions. [Deep Jive Interests]