In fire bug i see the following javascript error:
Error: syntax error
Source File: items_Insert.php
Line: 8, Column: 8
Source Code:
WAJA[0][] = new Array();
It looks like you have a record in the itemcategory table with a blank value in the MainCat_ID column that is causing the problem.
either filter the recordset to not include records with a blank value in the MainCat_ID column or remove those records from the database.