Today, both Firefox and Chrome have stopped opening any webpages at all, including local html files, or the settings page. The browsers' applications start but they won't display anything. Chrome starts and tries to go to the home page, but will only display a frowny face in the tab, and grays-out the window. Firefox opens and tries to go to the home page, but just displays a blank page and spins its wheels. Chrome complains about Norton and Adobe extensions crashing. I disabled those two extensions in Chrome, but it didn't fix the problems. If I turn off Malwarebytes, Chrome and Firefox run fine. Malwarebytes scan does not turn up any problems. MS Edge runs fine whether Malwarebytes is running or not. Most recent intentional software installs ( all automatic updates) were four days ago, but this problem just surfaced today.
Lenovo Yoga 3 Pro-1370
Windows 10 Pro; Version 1607; build 14393.1066
Malwarebytes 3.0.6.1469; component package version 1.0.96; Update package version 1.0.1735.
Also running Norton Security Suite, provided by my ISP. Last updated yesterday.
Thanks in advance for help with this