only 7 of my systems are running
Make sure the avast plugin is not disabled into MS Outlook:
Outlook 2007 > Tools > Trust center > Add-inns > Manage Disabled items.
Outlook 2003 > Help > About > Disabled items.
Outlook 2002 > Help > About Microsoft Outlook > Disabled items.
Outlook 2000 > Tools menu > Options > Other > Advanced Options > Add-In Manager.
As reported a lot of times, the message "The provider is waiting on the subsystem to start" will be shown there until you open MS Outlook.
The plugin will be enabled automatically after that, i.e., if Outlook is running you'll have the 8 providers of the Pro version running.