It works now. I did uninstall and re-installed the extension, deleted all files and started from scratch. After I applied an additional recordset to the result page, the js error did not come up and I was able to finish the e-cart button and then later create all checkout pages.
Everything seems to work except that I now receive a parse error for the confirm.php page on line 466 which is as follows:
Parse error: syntax error, unexpected '?' in /home/[myusername]/public_html/boutique/Products/confirm.php on line 466
The actual line 466 on the confirm.php page is:
$RecipArray[$CurIndex] = $row_<?php echo ((isset($_SESSION["eCartCheckoutForm_firstname"]))?$_SESSION["eCartCheckoutForm_firstname"]:"") ?>
Thanks a lot,