Dynamics CRM 2013 - Can't view Lookup options on Bulk Edit

We had a CRM 2011 instance that updated to 2013 and at first glance everything went well. However two seeming unrelated issues appears.

1. When clicking on a particular lookup an error was thrown.
2. When trying to do a Bulk Edit the Lookup options would not appear.

The problem in the end was related and (sadly) caused by me.

On change of a particular Lookup we created a custom view for another. This custom view called a small function that formatted special characters correctly. This caused an error in global.ashx which I of course presumes was Microsoft's fault!

The small function was using jQuery and this jQuery version now conflicts in 2013.

To fix this we used

My$ = jQuery.noConflict(true);

Then using My$ instead of $ fixed the issue and both errors went away. So if you have an issue with Lookups not displaying in 2013 that did not occur in 2011 this is worth investigating.