Running Norton Antivirus version 22.5.0.104 on my MS Vista machine.
Yesterday, July 6 2015, NAV suddenly popped up an "Action Required, Threats Detected" box, with 4 severity HIGH alerts. I thought that was odd, since I hadn't been doing anything on the machine, but I clicked "Apply all", without thinking too much about it. Big mistake. Pretty soon my machine crashed. After 3 hours of restarts, blue screens, and repeated runnings of Windows "Setup Repair", I have a semi-stable system again, with a couple of ongoing problems.
One file that was quarantined as a result of the "Apply all" action was wllogin.cab. I now realize that this is a setup file for Windows Live, which is a client program for Windows Hotmail, which I use. If I try to start Windows Live now, the system bluescreens, which will cost me possibly another hour repairing the system, so am avoiding the WL client for now. Will try to restore the wllogin.cab later, but am concerned that may cause another crash, so I'll wait on that.
Three other msi files are flagged, which have been on the machine since 2007, have been been flagged "based on malware heuristics." I believe these are from an old version of Cisco VPN client, which I no longer use, but now every time I reboot Windows tries to install Cisco VPN, which leads to the "Action Required" alert appearing, which may lead to another crash. Quite a mess. Disappointing, since I have been using Norton antivirus for many years, never a problem until this.