I am not sure this is the case but I believe the following is what is happening:
For a while they have been able to dispel select spells like true seeing, vision of the omniscient eye, and ultra vision. However, lately if I have one of these spells on my character, so long as one of those spells are active they are able to dispel any spell i.e aura of vitality, barkskin, etc, until one of the before mentioned spells are stripped away. Not positive on this, just my best guess after observing the behavior.