Hi there, this happened to us. We entered in to IVA March 2007, have made all payments until September when we could only afford to make half the payment, we cleared this with IP and they said:
1) thats fine, as long as we pay the half that we didint (£189) before out yearly review in March 2008.
They also said that IVA only fails if you fail to make any payments for 3months.
In exceptional circumstances you can apply for a payment break but this has to go to a variation meeting with your creditors.
I dont know about you but you feel terribly guilty when you dont pay it, even though you clear with your IP etc.....
It is really hard, but to be honest been in this IVA has made me and my husband so aware of our money situation. We now only have a cash account, and we work out our money every month, making sure all bills inc IVA go out of bank straight away. What i generally do is work out the money that needs to go out of bank on bills then take the remainder out in cash and that means we dont access our bank,(that covers bills) and what we have at home is to last us till end of month, for shopping, petrol etc....
take care