Searchnu has taken over google search

Hi.
Despite having Avast Internet Security I seem to have picked up a virus of some sort.

I have done a full system scan and it comes up clear but by search engine seems to have been taken over by “searchnu” . I have deleted it from the search options and reset google as my default search and as soon as I try to search it has re-appeared and set itself as default. This happens in Explorer, Chrome and Firefox.

Any advice or help would be appreciated

Thanks

Simon

Start a new topic in the virus and Worms section

Follow this guide and attach logs from, malwarebytes quick scan / OTL / aswMBR
http://forum.avast.com/index.php?topic=53253.0