The deployment in WORKGROUP enviroment is really complicated. There might be a different user at each computer (and probably is). Therefore you cannot deploy the clients just with one user/passwd. And the machines in workgroup might not be discovered or reached correctly sometimes.

From our experience it seems that the safest way of deployment in WORKGROUP enviroment will be the Email deployment(not there yet). You’ll sent email with download link to the users in your workgroup. And when they click it the installation starts. The user just runs it then it install automatically. When installation finishes the avast! client connects to the server.