This drove us nuts, so I figured I'd post it to save someone else some pain.  
Scenario:

View 1 is on Tab 1 (that is smartforms tab).  View 2 is on Tab 2.
You create a rule on View 1 that transfers data to View 2 (in our case into an editable list). 
Everything works great, except for the data does not transfer in IE 8.  In the bottom left corner of IE 8, you can click the javascript error and you will get the message shown in the subject of this post.

The fix:
Create a rule before you transfer the data to the editable list to "Go to Tab 2".  Then you can add the data to the editable list.  No more error.

I did create a ticket on this one, but it caused us enough of a headache that I thought I'd post.