Try a different homescreen first and see if you get the same result.
If you do (and I suspect you will) then it's a problem with your carrier. The Q just reports what the carrier tells it.
I've had this before with Bell Mobility. The fix for me was to call and leave myself a voice mail and when I checked and deleted that one it went back to showing zero.
If that doesn't work then call Alltel as it's their problem.