What a shame when your plants were doing so well. I wonder if it was slugs that devoured the pansies and clematis. After some wet weather (was it rainy?) you often find slug damage. I think you are correct in thinking that the Sevin caused burn on the pansies. Always be sure to rtead the instrucion label carefully before spraying. Some plants are quite susceptible to leaf burn, especially if they are growing in a sunny spot. I doubt that the plants that have been damaged with recover sufficiently to give you a good display. You would be wise to plant something else in the spot for the summer and then replant with pansies in the fall to overwinter or in the spring. Protect your plants from slugs next time.