Explorer.exe won't run in Windows 8.1

I originally had a problem with browsers, IE11 and Firefox, not connecting to the internet even though I had a good connection, could ping websites, and send and receive email.  After many trials, it turns out a malfunctioning version of Norton 360 was the culprit.  Once I got it uninstalled using Revo Uninstaller, the browsers functioned fine, but now other things are acting hinky.  Neither Windows Explorer nor This Computer will activate, although both work fine in safe mode.  In normal mode the icons will blink, then the screen refreshes with no activation.  Computer is Acer Aspire MS-583P-6637 running Windows 8.1.  I have run Ccleaner, Malwarebytes, and AVG antivirus and machine seems to be clean.