There are two things to check:
- If it's a server problem, there would likely be some kind of error in the logs for the service ($VCLOUD_HOME/logs/vcloud-container-info.log)
- If it's a client problem, make sure you're using a supported browser and have Flash installed. You might want to try clearing cookies and your cache (or use private browsing/incognito) and then attempt to access the UI.