PHP Error Fix * ASAP * and Duplicate Site To Additional Domain

Site is done with with errors - [login to view URL] The previous programmer programmed from scratch and it works great but there is an error when new products are added sometimes. Different browsers, different users - sometimes the error shows up, sometimes it doesn't. Only on [login to view URL] after submitting new item. It was just on Mozilla, but not also Explorer. There was javascript on this form, was removed, thought the error was fixed, but it's not. I need this fixed ASAP (as in within 24 hours). Shouldn't take longer than 1 hour for a PHP expert. This week, I need this entire site copied and pasted a new domain, tweaking any domain name changes within the programming so it runs smoothly on new domain. Should be easy work and easy money for this. If programmer fixes this issues and duplicates the site without problems, he/she will repeat the duplication at least once a month to different domains and will be paid each time. Please view the domain and ask questions before you bid. If you want to try out the site to look at the page with an error I will send you a coupon code so you can do this for free.