I've been figthing with this for some time now, with no joy. I found that somebody has an identical problem here: http://www.bleepingcomputer.com/forums/topic279534.html
So in any broswer (MSIE8, Firefox, Chrome etc), google search results are hijacked to searchwebnet.info, and then redirected to various other locations - e.g. it seems the first point is searchwebnet.info, and then my browser makes a couple of other hops, before it eventually lands on some dodgy site. Results from search engines other than Google (e.g. Yahoo! or Bing), are not hijacked.
Also, same as described in the topic above, MSIE sometimes doesn't start, or sometimes bluescreens my machine when I attempt to run it.
One thing I noticed, whether is relevant or not, when the redirection happens, in windows task manager I see SearchProtocolHost.exe process starting up. And staying there, running..
Interestingly, my problem also started happening around 17th Dec 2009, which is the date when the above topic was posted.
Any help is greatly appreciated!