Update:
Followed all the suggested steps and NO FIX for this issue.
Cleared the system cache, deleted all the saved data, deleted my gamertag profile and still no access to the multiplayer store.
On a side note, the store has never worked for me Z.
I have the digital deluxe version from the Xbox store, installed to the internal HDD.
Its weird because I can still play multiplayer matches and talk to other xbox users and they don't have this problem. In fact one time after a match, they talked to be while they were in the store and bough a chest. So i decieded to try and see if my store would work. It didn't. I could still voice chat with them though and had to say good bye since my game was then stuck in the infinite loading freeze of the store.