For the past two days I have received installation errors when I tried to install new apps in the Windows Store that is integrated into the Windows 8 Release Preview that Microsoft released some time ago. Before those two days, I had no issues installing or updating apps at all.
Whenever I clicked on the install, try or buy buttons, I received the message "Your purchase could not be completed. Something happened and your purchase can't be completed". No matter which app I tried to install in the store, or which option I did select, I always received the message that I posted above.
After I tried to install a good dozen or so apps in the store, which all failed with the same error message, I decided to go error hunting to find out why installations failed suddenly.
I first thought that this could be linked to the location that I had set up in the account, but switching to a different country did not change a thing.
After trying other fixes, like running scannow /sfc to check the system integrity, and even running a refresh, I finally discovered a working fix for the issue.
First thing I noticed was that the your apps listing did not display any apps when I tried to open it. When you are in store, you right-click and select Your Apps from the top menu. If you get an error message, you know something is not right with the linked Windows Live account.
This may not be the fasted way to fix the store error, but it did work for me, and it is likely working for you as well. When you are in the store, right-click and select Change PC settings in the lower right corner of the screen.
Switch to Users, and select to switch to a local account. If you are already using a local account, you may want to try switching to the Microsoft account first.
Once you have made the switch to a local account, you need to sign off and on again. When you now visit the Windows Store, you should be asked to enter a Microsoft Account username and password to sign in to the store. Once you have done that, application installs should work again. You can now also switch to a Microsoft Account again with losing the functionality.
So, what you basically need to do is either switch from the current account that you are using right now to the other possible option (from Microsoft account to local, or from local to Microsoft account).