Dollar sign in post

I’ve noticed that in my posts, when I use a $, it is dropping out and being replaced by a value. It works in the post title and the page title, but it’s being replaced in the post. It also looks ok in the edit window.

Other than using &#x24 does anyone know of a fix?

I made a sample of what I’m getting at http://www.rallycentral.us/archives/2005/02/26/dollar-missing/