I have Outlook 2007 Office Pro and Avast 4.8 Pro installed on Windows 7 operating system.
Have noticed when i look at the resident scanners that the outlook scanner says it is waiting for the subsystem to start but outlook is up and running - all other scanners are started
Make sure the avast plugin is not disabled into MS Outlook:
Outlook 2007 > Tools > Trust center > Add-inns > Manage Disabled items.
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.