There really should be a way to do this. I upgraded to WordPress 3.2 and had to downgrade to 3.1.4 because a plugin malfunctioned. I used this video on youtube to help me downgrade, but it was a fairly scary procedure (although not too difficult).
I definitely think there should be a simple way to roll-back your wordpress installation at least one iteration if you are having trouble with some of your plugins. And definitely notify the plugin developer of course.