As a temporary work around you should try updating the require once line on this page to be an include() function call. The path should not need to be updated. If the script thinks that the file has already been included adding this include should force it to try and include the file again. If you get an error about the file having already been included you can add an @ in front of it like this:
[php]
@include("WA_eCart/eCart1_PHP.php");
[/php
Please give this a try to see if you get past the problem. Post back and let us know how it goes.