A morph shouldn't effect the way ik behaves so... Maybe if you could show us a picture or describe the trouble more? Also are you using Poser 4 or 5? If it is a character INJ pose it may be changing the scaling of the figure and that could have an effect. Which pose is it?

"Your work is to keep cranking the flywheel that turns the gears that spin the belt in the engine of belief that keeps you and your desk in midair."

Annie Dillard