Need help with new nano-reef

[budocs]

I started a 29 gal. Nano back in September 2002 and until now, had few problems. The reef is (was?) home to 1 yellow Tonga leather, a few red mushrooms, 1 hammer, a few Florida ricordia polyps, some sun polyps and some star polyps. I also have a one cleaner shrimp, two peppermint shrimp, some blue leg and red leg hermits, 1 Mexican turbo snail, and an unknown (and uncatchable) as yet to be categorized white crab with red legs. I also have 1 yellow watchman and a dragon goby. My chemistry is always as follows: Ph 8.2-8.3, Ammonia 0, Nitrite 0, Nitrate 0, SG 1.024, Ca 380-410, Alk 3.8 - 4.5 m/eq, Temp 80. 5 days ago, I made two changes to the reef: I started a sump from an old 10 gal. Tank (after some tweaking and a few spills it worked well) and shortly after I introduced a then beautiful Green Sinularia to the reef. Within 15 minutes of introducing the Sinularia, all hell broke loose, though I didn't immediately recognize it as such. All of my corals closed up as tight as possible and the Sinularia began sliming profusely. I didn’t worry too much and shortly after, my last actinic went off and I went to bed. The next morning everything looked worse so I changed 10 gallons of water and started a carbon filter. By the next day, I had effectively changed all of the water, 3 times and then I returned the Sinularia to the LFS where I bought it. They proclaimed it dead. I had to go out of town and just returned and now everything else is dead. Except my crabs and fish. Even my plant life is dead. Stranger to me is that my protein skimmer isn’t picking up any nasty green sediment any more. I am in total shock and have had my water tested twice by the LFS, where the also agreed with my numbers as stated earlier in the monologue. Help! Though not new to fish in general, this is my first attempt at a reef and it appears to have just ended in total disaster and I am without a clue as to what happened.