VM is working on my voicemail right now...
Virgin is attempting to fix my "1 new voicemail" notification bug by quickly swapping my service back to my previous phone, clearing the voicemail, and then swapping me back to my evo. I'll let you know if this works and if it does and you're having the very common voicemail problem, I suggest getting right to the point with VM and telling them to do this same thing so you don't have to wait 2 or 3 days like many people are.
UPDATE - Finally, I am without the erroneous voicemail notification. This did work, so if you have this problem I highly suggest straight up telling VM to do this, otherwise they'll just run you through unnecessary and annoying troubleshooting steps.