Steps to solve windows  apps update and download problem:
Cancel the current installation from store>  Go to Desktop>  Go to charms bar> 
Click on Settings>  Click on Control Panel>  Click on Troubleshooter>
Click on Fix Problems With Windows Update under "System and Security">
In the new window click on Next> Click on Try troubleshooting as an administrator>
Close the troubleshooter>  Re-open your store and Install.
BEST OF LUCK !
See video tutorial  here-