Igor - I am having a similar problem. My e-mail client is Outlook 2003 SP1. It did not open properly a few days ago and had to be restarted in safe mode. Now it starts very slowly (as though it is looking for an add-in it cannot find). The Avast! logo never appears, and I have the same note (waiting for a subsystem to start) on the Outlook/Exchange Provider.
Make sure the avast plugin is not disabled into MS Outlook:
Outlook 2003 > Help > About > Disabled items
Outlook 2000 > Tools menu > Options > Other > Advanced Options > Add-In Manager.
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.