The same here as well. After the update I got the warnings, and thinking it was legit I clicked on the option to put the virus in the chest. First it said access denied then it said it needed to scan after a re-boot. So I allowed it to re-boot. It scanned and scanned and scanned my system making it seem like a virus had run amok. When it finally finished I ended up with over 40 so-called infected files in the chest.
Webroots SpySweeper and IObit 360 Security are now toast. A scan with Malwarebyte's, which was already installed, showed no problem. I figure MBAM wasn't affected because it doesn't update automatically or run in real time as SpySweeper and IObit do.
When I realized this had to be a false positive I tried restoring the files from the virus chest, but Avast would not cooperate. I highlighted each file one at a time and clicked restore but nothing happened. Judging from the postings in other forums this issue with Avast is wide-spread. I hope Avast will be able to post a solution on how to restore things back to they were. I for one cannot afford to take my PC in for repairs.