I just did some more testing - and this is very strange. I played with the settings similar to newguy and arjen with similar results. No change in behavior but here is something else:
If there is background noise on the callers phone, it does not stop the message after 2-3 seconds. If you call the number yourself, press a couple keys it will also continue with the message -- and afterwards it even works with quiet calls.
I called each of my numbers pressed OGM unassigned keys to get to the end of the message - and since none of the calls got dropped after 2-3 seconds any more. If you restart IVM - you have to call each number again to get it started. I also submitted a support request as I have 12 month email support.
Can anyone verify this?
Thanks.