I've had my phone for over a year and I have never before seen this notification, or whatever. The 172 and this little kinda voicemail looking like symbol. Didn't see it on the list of common BB notification symbols either.
It looks like a voicemail count, but it doesn't look like the default voicemail icon
Are you using any third-party voicemail apps? A bunch of undeleted voicemails? Have you tried a battery pull?