If your inventory is having problems loading this usually indicates that your console is having trouble reaching the inventory backend service. The most common way to fix this if it does not clear up on its own (due to a temporary outage of the backend) is to:
- Turn your console completely off
- Wait 20 seconds to several minutes
- Turn your console back on
Other causes include a network block or slowdown from something like a firewall on a router, or packet loss from a wireless connection.