If you can continue to make payments the IVA will carry on, if you cannot make payments it will fail. If you are most of the way through and leaving work isn't voluntary the creditors might accept payments to date, or agree an extended break until you find more work.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014