I agree, this is really annoying.
But, today is Sunday, maybe tomorrow morning you can get some help from the programmers of avast! It seems that a drive (Microsoft’s one perhaps) is not interacting well with avast!
Can you low the sensitivity to Normal (Standard Shield)? Does this make any difference?
If not, can you disable the Resident providers for a while to see if they work when re-enabled?
You are free to change your antivirus, but try to find a better support than avast! ;D