I'm on 8.x not 9.x so I'm not positive if the same issues carry over, but we have a Cisco Comm Mgr setup as well as a Nortel SL100 and Cisco Unity VM, and we have to be very careful about the number of digits that we are sending from one system to the other. Our extensions in Cisco are 5-digits, so we have 5-digit mailbox numbers, but Nortel sends full 10 digits to Unity VM, so we had to create Alternate Extensions for all of our Nortel users in Cisco with the full 10 digits listed. That way when Unity answers and sees the 10 digits it knows which 5-digit mailbox greeting to play. You can use the port monitor in RTMT for Unity to look at the numbers being passed and verify if that is the problem.