system
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Have dealt with this issue on several small business networks in the last few days. All were peer networks with a Win7 pro machine holding a database for some specialized application, or quickbooks, or files, etc. These networks and their sharing have been stable for a very long time. Avast 2014 update to file server prevented sharing - couldn’t even ping the server in all cases. Tried many variations of settings described here and elsewhere. No good. The only solution was to uninstall (aswclear in 2 cases) Avast and put Free version back in place of IS. Everything worked immediately after that.