Thanks for the reply,

cleared invoices, cookies and the cache and we still seem to have a problem. Here's an example. In the products and services screen the item shows as a QOH of -1. When I go into the stock adjustment function to set the value to 0 the QOH displays as 0.
The sctock adjustment screen value is correct but it's causing problems with invoicing as it shows the incorrect QOH value.
I've added a couple of grabs to show what I mean.
I'm using Quickbooks on a Mac with Firefox but also tried opening in Safari and got the same incorrect QOH.