It's probably an issue with the call handler you have 1 setup to go to, not your opening greeting configuration. I'll be the owner or the recipient of the target call handler is missing (i.e. you had it setup for a user or DL that's now no longer in the system). That's the most common problem I see here...
you can check the Application event log for errors when you get the failsafe conversation there - it will say why the conversation booted you out and confirm. You can also download the latest dbWalker version from www.CiscoUnityTools.com and run it - it'll fiind most handler configuration problems, although my money is on the administrator/recipient link being broken.
