I've been getting this problem for a month or two now; if I enter a url I see it in the address bar, however, I see a bunch of adlinks instead of the expected site. Here is an example;

http://www.revenews.com/samharrelson/2006/12/infected_linux_via_cpa_network.html

I have tried various spyware scans, online virus scanners [we use Trendmicro here]. Rootkit Revealer only found a couple of Flash files. It seems quite random as to what sites get affected but when they do there's a change to the base href when I view the page source to '*/common/roar/landing/rpos/'

I've googled this a fair bit without much success other than a few 2/3 year-old links.