I've never experienced this, even with Poser 7. I might be doing it differently though; I loaded a V4, turned off IK, added the Morphs++ then saved her as a different figure (V4 Morphs++). If I load original figure (V4) she has the IK; if I load V4Morphs++ she doesn't have IK.

 

Maybe try saving under another name (like V4 noIK).