Avast 18.6.2349 causing connectivity problems after upgrade of Avast antivirus product. Malwarebytes users also reporting problems after upgrading Avast. Avast’s antivirus program is causing problems with Malwarebyte’s web protection module. Users are advised to disable a protection module from one of the programs in order to avoid the conflicts. Malewarebytes is working with Avast/AVG to resolve these issues, but has not yet provided a time frame for the fix.
Source: https://www.bleepingcomputer.com/news/security/avast-users-having-internet-issues-and-malwarebytes-conflicts-after-upgrade/