I've sent the test scene, but I've got an interesting new result. 

Apparently the texture crosstalk is only occurring if I select the option to allow re-posing inside Vue when I import the Poser scene.  I have been leaving that option selected the whole time and didn't think to try to disable it until now.  I don't see anything in the SkinVue user guide indicating that this option should not be selected, so I'm assuming that this is not normal.  But it's definite progress.  If I uncheck the reposing option, the SkinVue modifier works just fine on both characters in the same scene.  I've revalidated this with 4 separate scenes now with the same results each time.

allow re-posing = texture crosstalk
disallow re-posing = all's well