I had a similar problem, and in contacting two different people at Microsoft, the fix was a hard reset. Right now I've got a problem where it constantly shows 1 update more than what there is on the live tile (so when there are zero updates, it shows a 1). Being OCD like I am, I keep tapping, and when I go to the store where there are no updates for my phone, it goes away for a little while, but it comes back. I'm hoping that 1) we get Portico soon, and 2) that it will fix it. If not, another hard reset.
Fortunately, hard resets now aren't as terrible as they used to be. I did two in one weekend a month or so ago. Make sure you back up your app list first, in the settings, then go at it. Most apps will automatically reinstall, with a couple exceptions that waited about 18-20 hours before I got notification of (Nokia Extras + Info, for example), but the only thing lost is app data - game progress for example. Since I'm not a gamer, that's not a big deal to me.
If it really bothers you, go for the hard reset. If you want your start screen laid out the same, take a screenshot first, and make sure it either syncs to your computer or to Skydrive. Go into the Phone Backup in Settings, back up your app list, and go for it. If it's only a minor inconvenience to you, wait to see if Portico fixes it.