Would it be possible for you to post a screenshot so we can see exactly what's happening?

Just off the top of my head, it sounds like there might be a rigging error. Since you're rigging clothing, you probably know that you have to make body parts in the clothing that match the body parts of the figure who is going to wear it. The body parts are parented to each other, for example:

Right and Left Shoulders are parented to their respective collars, which are both parented to the Chest, which is parented to the Waist, which is parented to the Abdomen, which is parented to the Hips.

In Poser at least, two body parts cannot touch each other unless one is directly parented to each other. Here is a quick drawing I did to clarify:

In this drawing, red represents the Hips, blue represents the Waist, purple represents the Abdomen, yellow represents the Chest, green represents the two collars (right and left), and pink represents the two shoulders.

The shirt on the left is rigged properly. Notice how no two body parts touch unless one is directly parented to the other? The shirt on the right is not rigged properly; the Shoulders touch the Chest (circled in red), but the Shoulders aren't parented to the Chest, they're parented to the Collar. This shirt will "tear" along the joins between the Shoulders and the Chest.

Does that help? If you need more clarification, just ask