Is there a big difference in seo value between a link to your site from another on the same server, compared to a link to your site from one on a different server and totally different IP?
Yeah, there's definitely less valuable backlink value from something on the same ip/server. Can't say how much exactly though.
Different Class C Ips are better than Similar Ips, and are extreamly important for Google and Other search engines especially msn.com
means if we had for example, 5 sites hosted in one dedicated server with same ip, if i link all the sites to my blog, its counted as one backlink or 3 backlinks?
Don't you mean one or 5 backlinks? It would count as 5 backlinks, they'd just be of less value than from a different Ip/Server.