Thanks for the replies. There was an update available for ModernMix so I did update that. I also opened ModernMix and noticed the Store app was set to Maximized so I changed it to Windowed. After about 24 hours or so now, the Store app seems to have stopped opening. I am guessing the ModernMix update did the trick.
With that said, I did notice one other quirk/glitch. Since installing the Windows 8.1 update, I also cannot drag/move any of my Desktop icons. For ex, I have some program shortcut icons, MS Word files, PDF's, etc on my desktop and I cannot reorganize them. If I add a new file to my desktop, it automatically goes to the first available spot on the top-left and then it is stuck there. I can click and double-click on any of them with no problem to open files or programs and I can also click on them and delete them with no trouble. It is only the dragging/moving that does not work. If I try to drag and icon, the cursor changes to a black circle with a line through it.
I have Fences, ModernMix, Start8, and WindowFX installed and I updated each of them and rebooted, but that did not resolve it. Do you have any suggestions for that? Thanks.