When using Omnisphere within Live 8.04 on a Mac, I have Omnisphere setup on a midi track and in "Live Mode". Using Program Change messages to change patches, Live mode doesn't turn off the previous patch unless the plug-in window is turned on (at least once). Resulting in all patches to be activated as you move through the patch list. I forget which is latch and touch mode, but it works fine once you activate the plug in window.
This is obviously a problem as I don't want to click on unnecessary windows as I switch Live Sets.