I just figured this one out - after using all the spyware apps I could find, this is what did it:
Download "HijackThis" (I know, terrible name):http://free.antivirus.com/hijackthis/
Let it do a scan, and it'll find a bunch of stuff, but look for lines that look like this:
HOST (ip address) google.com
HOST (ip address) google.com.it
HOST (ip address) bing.com
I found about 20 of them. Check these lines, and have HijackThis remove ONLY those. That immediately fixed the problem for me.