When we looked at the jQuery include I noticed he was using the latest version from the Microsoft CDN, which happens to be version 2.x. Because I had another site running with jQuery and Knockout I had him revert his version of jQuery to 1.10.x and we found this was working.
The cause of the issue is detailed in the jQuery documentation for 2.x:
jQuery 2.x has the same API as jQuery 1.x, but does not support Internet Explorer 6, 7, or 8. (source)
The reason this is relevant is because SharePoint masterpages include:
Which forces IE browsers to effectively run in an IE 8 mode.
Therefore, if you are a SharePoint 2010 developer and are attempting to use jQuery, make sure you are using 1.x versions