It looks like you are missing a column:
ITEM;ITEM_CODE;STOCK_ID;Description;Category;units;dummy;MB_FLAG;Currency;Price;
Where Item_Code = STOCK_ID of the item.
You have the STOCK_ID missing
I think for the most part ITEM_CODE == STOCK_ID, these are used in the 'item_codes' table
Also line 52 of import_items.php has a problem it should be:
function get_dimension_by_name($name) {
if ($name == '') return 0;
it was
if ($name = '') return 0;
If you are using dimensions, it seems that the 'dummy' field before MB_FLAG is where you can put a dimension
Let me know if this fixes you up
tom