It could equally apply to Avast's firewall.
See if you get the same error in Safe Mode with Networking - 3rd party security programs are isolated in that mode, which is safer than trying it with Avast disabled.
I'm not sure how you use the restore points in Win 8.1 but going back to prior the error could pre-date an Avast Definitions update, as it won't be the first time a security program's updates have caused problems.