I said I'd post my findings and here they are. I had x-cart look into the problem and they found a bug in the version 4.0.12
Here is the response from x-cart:
Code:
To fix the bug please apply the following patches
DIFF_17077.patch
DIFF_17317.patch
The patches can be downloaded from "File Area" -> "My Files" section of your personal Helpdesk.
Thanks Padraic for your help.