I was ranked #2 for a few keywords, and in one day I completely dissapeared, I was using COOP, and I've been doing some reading, and it looks like its because of so many "spam/crap/unuseful sites" using COOP and abusing it which caused it to happen to me. I don't run a crappy site but I'm in the genre of a lot of people trying to get up there and probably abusing it. MySpaceSupport.com, anyone have suggestions for getting ranked high again in Google? SEO tips, anything, thanks!
Well, the good news is that a lot of your pages are still indexed by Google, so it is probably just a temporary thing. Google is known to do that a lot. If you have not used any "black hat" techniques, you will reappear very soon. My website (see my sig) is like that a lot too...I was ranked #1 for a good keyword with 17.5 million results, and now it is gone. Usually it happens, when Google is about to reindex my site. I am sure there are others that know much more about this than me, so I will let them help you out as well
Have you checked your outbound links? Make sure you're not linking to any site banned by google or classified as "bad neighbours". It could be a temporary thing as jdw4jesus noted, try the multiple datacenter position checker. You could also check the backlinks for sites that are on top now to see if you need to work on backlinks.