This means that the provider Outlook/Exchange waits for Outlook to start. Also this provider is for MS Outlook and MS Exchange mail clients only.If you don’t use them you can shut down the provider.
So the subsystem for this provider is MS Outlook or MS Exchange.
As said before, 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. In fact it’s a plugin and not a ‘provider’ 8)
Right click the avast icon in system tray → Choose “Program Settings” → De-select “Enable skins for simple user interface” → Close all avast! windows and then re-open it. Hope that works better for you; if not, just undo the actions and look for another skin here: http://www.avast.com/eng/skins.html