This indicates that IP change has some effect on indexing.. I think Google indexes sites based on IP's also @jhnrang whether that was a dedicated server (your last host)?
I think hosting have something to do with PR too, something similar have happen to me too as a result of changing server.
You might need to check your backlinks, maybe you have lost one of the quality links linking to you... or simply those links dropped in their pr
I always get a dedicated IP for any shared hosting account. Everyone tells me it does not matter. I think that if you do not have your own IP and another site on the server is banned by the SE's, it could reflect on your site.