position:fixed not working in Google Chrome
try adding the following code to your element:
-webkit-transform: translateZ(0);
I had a property: -webkit-perspective:800; on the body tag. I removed this and the fixed positioning started working again... obscure, but worth a look.
As an addition to the won answer: this would not work if you have "-webkit-transform-style: preserve-3d" in one of the parent elements. I don't know why, I just had such and removed it.