Error editing eCart 3 with eCart 4

I have an older site that was build with eCart 3. I need to update the shopping cart with a discount. Any edits to anything in the store throws the following error on the shopping cart.

Microsoft JScript runtime error '800a138f'

Object expected

/copperscapes/shoppingcart.asp, line 236

Line 236 reads
<td align="right" class="S3B_OrderLineItem"><%=WA_eCart_DisplayMoney(CSCart, WAEC_NCStateSalesTax())%></td>

So something has changed in the way the taxed are handled.

What is the best way to fix this, without killing everything and starting over...which nobody will pay for.

If this is on the cart display page it may be best to just create a new cart display on the page and remove the one that is having problems. Have you upgraded the cart object to use the newer version?

I have not updated anything. Is there a specific process/steps that I should follow or just redo everything?

The things that you may need to update if you use the new eCart are the cart display, and anywhere on the site where there is a reference to the charge rules, specifically the taxes and shipping.

Other than this your old cart should work with eCart 4. It is always best practice to make a copy of the files for the site before you update them.