'tagName' is null or not an object

I just upgraded from G2 to G3 and migrated all of my data a couple of days ago and am seeing an issue that I would appreciate some help on...

In IE8 on Windows 7, whenever I navigate to my gallery and select any item from the Options menu in the bottom left corner of an album, I get the yellow "Error on Page" notification in the bottom left corner if IE8. When I click on the notification for more detail I see the following:

Errors on this webpage might cause it to work incorrectly

'tagName is null or not an object
index.php/ Line:73
'tagName' is null r not an object
index.php/ Line: 73
Code:0 Char:4
URI:http://{mywebsite}/Gallery3/index.php

Everything works fine if I use Firefox, or if I use IE8 on another PC.

Any advice on how to move forward from here would be appreciated.

Thanks in advance.