I seem to recall from the help files of an old version of Poser the instruction was not to toggle ik's, use them or don't, switching will give weird results. With ik on you are setting specific xyz co-ordinates for the hand and the arm joints are forced to follow them (in fact the software has to guess where to put them, so the position and rotation might not be true to life), if you turn them off, the hand will try to stay in the position set whilst the arm joints will revert to their bend/twist/side to side parameters so the hand may be forced into weird angles. One solution is to break your animation down into parallel .pz3's then cut the renders together in video editing.
Below is a link to a vid I made a while back, parenting the poser mannequin's hand and feet ik's to another figure (D3) Many weird things happened especially as it seems that ik's get really confused by rotations of more than 180 degrees. The simplicity of the mannequin figure made it easier to disguise grotesquely twisted limbs, when I tried to repeat the experiment with a human figure it became impossible.

http://www.youtube.com/watch?v=L0JxiNdqdRI&feature=channel_page