Example included for better understanding:

http://jsfiddle.net/3xBcy/

<table class="grid" border="1">
    <tr>
        <th>Column 1</th>
        <th>Column 2</th>
    </tr>
    <tr>
        <td>Content 1</td>
        <td>Content 2</td>
    </tr>
</table>

I try to get the TABLE tag with a parent function

var table = $('.grid tr:first').parent();

This means, get the parent of the first line from a table with the class "grid" assigned to it ("$('.grid table)" won't work btw.), which is the table itself.

Now trying to wrap the table in a DIV tag fails in IE 8 and ends up with a strange behavior in Mozilla.

table.wrap(div); 

But if you try to do the same with

$('table').wrap(div);

everything is fine ...

The variable "table" seems to be a valid element. This code work:

table.hide(1000);