two jQuery UI datepickers in one form, 'missing instance data'

Easy to solve, change your code to something like this:

$('.date').live('focus', function(){
    $(this).datepicker({
        changeMonth: true,
        changeYear: true,
        yearRange: '1930:'+(new Date).getFullYear()
    });
});

Two things come to mind:

One is in your jQuery selectors:

jQuery('input#copyFrom','div#copyFromHistory form')
jQuery('input#copyTo','div#copyFromHistory form')

In both cases you pass the context/ownerDocument parameter to jQuery() but that is looking for DOM element or document... not a string.

And the second thing is:

Copy From <input id="copyFrom" name="copyFrom"/>
Copy To <input type="text" id="copyTo" name="copyTo"/>

Copy To has type="test" and Copy From does not (though the default input type is text... so probably not that)

I suspect you really want:

jQuery('input#copyFrom').datepicker(....)
jQuery('input#copyTo').datepicker(....)