Neither MBAM or DrWeb CurIt should conflict with avast, though you don't have to, I would always pause the standard shield when doing a scan with another security program. You may possibly have an infection that is attacking avast, but that isn't by any means certain.
What avast processes are running in Task Manager, they begin with ash or asw, see image ?
MBAM doesn't directly say Quarantine, it says Remove Selected, it removes the original but a copy is placed in quarantine.
You don't say what the file name or location is, you should be getting used to this routine interrogation
it helps us to help you.
Try a repair of avast. Add Remove programs, select 'avast! Anti-Virus,' click the Change/Remove button and scroll down to Repair, click next and follow.