This is a huge problem. There is long thread at Windows 8 Store Won't Open? - Microsoft Community
Still unsolved. I replied there and want to repeat it here.. to spread the word
Microsoft, could you please wake up?! Obviously many users can NOT access the Windows Store, let beside no other 'App' starts, not 'Finance', not 'Weather', nothing. All the 'suggestions' are, sorry, bullshit. The best one can expect is to not break the system completely. Do not try any of this, it does not work. The problem lies much deeper and is not fixable by registry editing, dll-register, new user account, fonts,... blaba. ONLY MICROSOFT CAN COME UP WITH A FIX.