We're seeing an issue in Chrome Version 22.0.1229.79 m (latest as of writing this) that a <select> tag with the ui-helper-hidden-accessible class applied inside an absolutely or relatively positioned container is not being hidden.

The problem happens because the style is applying left: -99999999px; which appears to be too large of a number and is reverting it to left: 0px;, left justifying it with the inside of its parent that is absolutely or relatively positioned.

The offending line is

.ui-helper-hidden-accessible { position: absolute; left: -99999999px; }

in file

http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.2/themes/redmond/jquery-ui.css

This only appears to happen in Chrome, but similarly it only happens with this class (the others have smaller values for the left positioning.)

The largest number that appears to work in Chrome is: left: -35789999px;

I will also attempt to file this as a Chrome bug as well, but in the meantime jQuery is causing it to happen by having a value that's too large.