Its a common failure for webmasters to purchase a server and to locate both main site and satellite sites on it. The satellite sites need to send the links and traffic to the main site, but if they are on the same IP, the search engines gives it lower rank. Try to use free hosting or use several IP's for the satellite sites, keep the main site on the strongest server. Good luck
Agreed, there are also many SEO Hositng services popping up that provide separate C Class IP's to mix things up. This makes it appear that the hosting is spread around and helps build your link juice. Sick
In my experience it is mostly about single IP meaning all the sites are hosted on the same static IP and are heavily interlinked together. You can use the same server and still ask for more static IP's from your host. They most of the time charge from $1-$2 per IP/month. Now you can host multiple sites on different IPs and same server. Another option could be to use VPS which are low cost virtual servers and use them on geographically distant locations with different IPs and then interlink your sites