**UPDATE**
I have finally been able to see this issue elsewhere and after intensive testing this morning have come to the conclusion that it is a hosting issue.
So could you contact your hosting company and mention that you have a
problem with a form. The form has 5 arrays, each of which can be upto
250 in size (its actually only around 180 atm) and the $_POST array
truncates before it gets to the submit at the end of the form.
The form has these arrays: code, zone, country, list, delete
+ the one submit at the end of the form.
If they do happen to change something and it starts working again, I'd really appreciate knowing what they tweaked.