Just thought I might save people some time. Jan 19th I installed a recommended windows update KB2858725 (Microsoft .NET Framework 4.5.1
This was on my mothers HP system with Vista. After a reboot, it wouldn’t connect to the internet (chrome, IE etc). Kept saying no network was detected. I deleted and reinstalled the network driver via a laptop and usb stick. Tried Microsoft suggestions of a NetFxRepairTool. Deleted this new update. Tried KB2858728. Tried the old 3.5 version. Nothing seemed to work after hours of attempts. I had not changed anything else that day so I gave up. She took it to a repair shop and they said after they removed Avast, it worked just fine.
I can’t tell you the version of Avast, but it would have been the current Free one for Jan 19th as she updates as soon as she’s notified to (I removed all traces of Norton long ago and she had no other antivirus or firewalls installed). They installed a different antivirus now so not sure if a reinstall would have worked on it or not.
Just an fyi
No problems here with KB2858725 (.NET Framework 4.5.1) and Avast Free 2014.9.0.2013,Windows 7 x86.