Thousand-minute voicemails

Just re-installed Asterisk a couple of weeks ago and am having a weird problem. Twice now, when I pick up the phone, I hear white noise (assume some kind of data link?). When I download voicemail, my Asterisk tells me the current message is huge, typically 600-1000 minutes long, and its the phone company telling me that the number I’ve dialed does not exist. In other words, Asterisk seems to be phoning out then not disconnecting.
This sound familiar to anyone?