Sometimes problems can occur with AVs. Has yours just had an update? What I've read is problems with Avast, McAfee and Kaspersky. The usual solution was to use the respective removal tool for the AV, usually in safe mode, then run on Windows 8's Defender for a while. If the apps open OK when using Defender then your AV might be the problem. If not you can always reinstall. You can also try the system file checker, option 2 here.I would not consider a 'Refresh' of windows 8 as that will remove all your installed programs from disc or online.
Microsoft Lumia 950 vs Lumia 950 XL: What's the difference between Lumia 950 & 950 XL?