Mac App Store application no longer opens

Hi... I've seen others say this, in both old and new comments, but without any solutions other than reinstalling OS X.

Summary: My Mac App Store application no longer opens. Not even to give a blank screen.

When I click on it in the doc, it hops once and then stops. Nothing after that.

And if I select "Software Update..." from the Apple menu, no go there either. Nada.

I'm running Mavericks and was trying to install the 10.9.2 update at the time.

I was able to do this, but only by going to the Apple website and downloading the disk image from there. Hasn't fixed the App Store though.

Anybody have any ideas?

Thanks!