Two quick things to note: for arms and legs to behave anywhere near predictably with IK, you want to try to limit the number of joints in the IK chain to three whenever possible. For instance, if you look at a lot of human figures you'll find the IK chains look like shldr>forearm>hand and thigh>shin>foot.  From time to time I've built figures with ankles or wrists and added those in, but the most successful instances of that are when the figure's default shape is designed with a little bit of a bend in those joints already in place.  Also, when animating with IK, I've found that you have to be extremely careful about whether you turn it off and on while working. If you move down the timeline in an empty scene, move something with IK and then turn IK off, when you look in the keyframe editor, you'll see that keys were created for EVERYTHING on that chain.  Think of it this way: when you move an arm based with IK, the hand controls all the arm's parts; what you have then set a keyframe for is not only the rotations of the hand, but it's translations. If you animate without IK, or turn IK off while animating, then you're animating strictly via rotations and since no translational keys are set for the ik handle when you animate that way, you can run into problems.

Another thing to consider, though it's only in newer versions of Poser, is to use animation layers. With these you can blend clips of animation together and make a lot of broad sweeping adjustments pretty easily. One major user I've found for animation layers is to animate a pass of movement using IK, then add a layer on top of that without IK, animate secondary animation there and then adjust the blending of the two.

Hopfeully some of that might help. -Les