I was facing the same problem in windows 10.Yeah, it's the known Sophos incompatibility issue.
Go into AG's Settings > General Settings section and scroll down to the bottom and click on Advanced Settings. Then scroll down again to the bottom and uncheck the Use localhost for injections box, press Save and it *should* work fine again. Alternately you can go into AG's Settings > General Settings and change the update channel to Nightly (which contains a fix for this issue too) and check for updates. Otherwise, the Sophos incompatibility issue will be fixed in the next AG for Windows update.
EDIT: Got the setting mixed up, so fixed the instructions above.