"member cannot be found" error - help!

[leadman]

I added a bunch of hidden input fields to a form and now when i try to get to the page i get an error that seems to be related to the shopping cart session variable. The error is this:

===============error message start====================
The member "" in dimension 1 of object "session.cart" cannot be found. Please, modify the member name.

The error occurred while evaluating the expression:

#session.cart[2]#

The error occurred while processing an element with a general identifier of (#session.cart[2]#), occupying document position (123:69) to (123:88).
==============error message end=======================

Line 123 is just this (the exact same code works fine on my "viewcart" page, the products in session.cart show up fine on the page):

<input type=&quot;hidden&quot;
name=&quot;name&quot; value=&quot;#session.cart[2]#&quot;>