Adding Products throws the whole webste out

Hi all

I've got 2 laptops and a pc, i tried to add products to one of my websites this weekend on the pc and everytime i added a product the whole of the middle of the page disappeared and the left hand column ended up in the middle of the screen. If i then put this item out of stock (red box) then the website goes back to normal.
I then tried to add the same product as a new listing on my laptop, added no problems and looks perfect on the live site.

I'm guessing that there is a program i'm using that zen doesn't like but where do i start ...

Update ..... the following night i've tried to add more products on my 2nd laptop, same thing happened as it did on the pc so i thought, ok i'll go back to the first laptop and add the products from there. This time that laptop throws the left column to the middle of the screen and will only go back to normal when i disable that product.

I'm at a loss. I've not changed alot on the website recently, have reasonably little experience with zen so i don't play too far, i only change the things i know what i'm really messing with.

Please can anyone suggest anything to try to get this problem solved, i'm not even sure if its a program problem, laptop problem, website problem, coding or zen ....

Hope someone can help,

Thanks in advance Dave

Can't seem to replicate your symptoms.

If your many computers work consistently fine on all other websites, then perhaps something in your code is mangled. I'd start by inspecting every way in which your site differs from original Zen Cart code, since those are likely the culprit. http://www.zen-cart.com/wiki/index.php/Troubleshoot_-_Diagnosing_Obscure_Issues