If peoples facts were accurate then I would never have changed IPs, knowing that I would lose about $6000 in one month of profit. However, I asked many so called experts and everyone said "It is not a problem, nothing will happen. Go ahead and change IPs" Well...all you experts, you are officially very wrong and I would love for that Matt Cutts guy to see this thread. We never changed anything on the site. It was a straight changeover that took about 15 minutes to complete. If I could go back, I would have never changed anything and left it where it was. I would go back to the original but who knows what that might do now. Lesson for everyone.....NEVER EVER CHANGE IPS ADDRESSES ....unless you have a brand new site or don't depend on organic traffic.
It is possible that google changed their algo while you changed ip so it seemed like changing ip might be the cause when in fact it is something else. Some companies change web host and they never had this problem
google says it does not affect anything,but im not so sure.Im about to change servers,and my IP will change as well.may hold off on it
May be you moved from a dedicated IP to a shared IP one so Google thinks you are part of a spammy lot holding out in shared hosting dens. Other than that, the cause may be DNS down time, as mentioned in this thread, but I dont think that could be a factor, because you are still indexed. If DNS were down, then Google is going to try again in intervals, and you can always set the crawl rate in google webmaster tools.
I don't know why it happened with you but few days ago when I purchased a dedicated IP for my site nothing bad happend to me. My site is doing even better now, alexa is increasing very fast and google is indexing new pages much faster than before.
Unless I hear more other cases like that, I would say that there may be some other reasons for your site to drop in serps. Is your new hosting sever stable? If googlebots cannot reach your site, the serp rankings may drop too.
I had the same issue with one of the e-commerce site of my client. I changed the hosting without knowing the consequences it can have on ranking. He lost all the rankings for 4 weeks, although due to DNS change the site was down for more than 72 hours. I think you should wait for Google to get you the rankings back. Just my 2 cents.