I dont know where you get that idea from MalwareBytes is not an anti virus program it is basically a program designed to detect and remove infections that most antivirus programs tend to miss or are unable to remove. MalwareBytes is designed to work along side your existing antivirus software , not conflict or compete with it . So, if there is now a problem with Avast installation its because Avast is trying to replicate Malwarebytes! Not the other way around.