Internal Server Error when Clicking Next in Cart

I have a Hikashop I was about to launch but now have an "Internal Server Error" displayed when I click on the "Next" button of the cart. I have not figured out what change I made is causing this error.

The server log shows two clues:

"PHP Notice: Trying to get property of non-object in administrator/components/com_hikashop/classes/field.php on line 694,"

which I looked up:
function getFieldName($field){
return '<label for="'.$this->prefix.$field->field_namekey.$this->suffix.'">'.$this->trans($field->field_realname).'</label>';
}

"PHP Notice: Undefined property: ProductViewProduct::$rows in administrator/components/com_hikashop/views/product/tmpl/variant.php on line 23,"

which I also looked up:
<input type="checkbox" name="toggle" value="" onclick="checkAll(<?php echo count($this->rows); ?>);" />


The last changes I was making was unpublishing all country zones except for the United States (only shipping to the US). I also tried adding a Characteristics but decided it would not do what I was thinking and did not finishing saving it.

Any ideas? I would really like to get the site up. I have already tried uninstalling and reinstalling Hikashop -- must be an issue in the database someplace.

Thanks!

Thanks for the info. I turned error reporting on but I don't' see any errors displayed before the "Internal Server Error" page.

I think the fastest approach is to do a clean reinstall of HikaShop. What do I need to remove from the database and the file system to make this happen -- an uninstall of Hikashop was not sufficient.

Thanks

Thank you -- that worked and I have reinstalled and new configuration is working.