Russia probes social network chief over protests 249 words 9 December 2011 16:51 Agence France Presse AFPR English Copyright Agence France-Presse. 2011 All reproduction and presentation rights reserved. The head of one of Russia's most popular social networks said Friday he had been called in for questioning by prosecutors after refusing to deny access to several opposition groups. V Kontakte (In Contact) chief Pavel Durov -- whose Internet platform has been dubbed the Russian version of Facebook -- posted…