Not on the face of it -- but, if you have enough spare cash to put away a useful ISA contribution your I&E has not been calculated correctly and you could see your payments to the IVA increase if and when the IP realises.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014 http://foggy.blogs.iva.co.uk