Regarding the permissions, I found this page helpful: https://www.blackberry.com/blackberr...eo/sendAs.html
( but, it is working anyway now)
Regarding your poweroutage:
stop all blackberry services, then, start them in the following order:
all other BlackBerry Enterprise Server services
Does is work then ?
If during the startup the microsoft exchange server starts too late, the blackberry server might not be able to connect to the exchange server when it is ready