I am new here, because I am having this very same problem. Have 3 PCs connected via WiFi to LinkSys Router. only one PC of these (mine) is using Avast I.S. The other two are using free protection, and are both having no problems. But mine with A.I.S. is only able to connect to the WWW by disabling Avast, once connected I can then re-enable Avast protection. My renewal comes up early next year, so hope there is a cure on its way. Have tried all possible exclusions with no success.
PS........Also this verification used to post, surely is not required. My vision and hearing are impaired, and I have great difficulty in deciphering this gobble-de-gook!