rachel123 - 9:23 pm on Feb 28, 2011 (gmt 0)
They sound like standard bot attacks. Thousands of malicious links aren't planted by a person, they are planted by a bot.
Im a bit concerned about ranking aswell if I change hosts.
I'd be much more concerned about losing ranking based on a compromised site. Google will blacklist you for Malware if they find it, and with what you are describing, they have probably found it.
Done correctly, a server change will not damage your rankings at all.