I was in exactly same situation and was using Avast. Now contacted MS Support on Twitter and they are looking at it.
I use McAfee total protection.
I then uninstalled McAfee and installed Win8, didn't work (STORE fails).
Then I also uninstalled Java and again installed Win8, again didn't work.
All installations were using option of retaining existing software/apps and personal data and settings. After installation I did refresh installation which removed all software/apps except windows apps, it didn't work.
I had a backup of the original partition image so I could repeat the process from the exact condition of original Win7.
Someone above has successfully installed by clean installation removing existing settings, I wonder what existing software/setting might be blocking the STORE and Games to be installed properly.
I will try to do a Clean Installation, I am expecting it will work.
But then again what is the current apps/software/setting that might block the proper installation.
(I am not happy removing all current settings and installations, I have loads of current software and settings. I mean really a lot. And some of them cannot be reproduced and time dependent)
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