Remove Oneclickads Pop-up Page - Get Rid of Oneclickads.net Redirect

When I click on any browser link (in Chrome or Firefox) a new tab opens to a oneclickads page that then redirects to an unwanted ad page. AVG Internet Security did not warn me when it downloaded and a scan does not find any problems, two free malware programs I downloaded did not work and none of the suggested manual processes suggested at various sites work either - e.g. there are no suspicious programs listed on Windows Programs to delete, there are no suspicious extensions in either browser to delete. Can anyone help?

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