My apologies for resurrecting this thread, but I have at last managed to identify the Windows 8 cause. It is the horribly buggy Windows 8 TimeBroker Service. The following Microsoft Forum thread takes you through the symptoms. (Usual effect which can be viewed through the Resource Monitor is to eat network and cpu resouces)
As I have been unable to identify the offending Live Tile apps I have 'zapped' TimeBroker via the registry using the methods described in the thread:
... hope the following link will help:http://nlabs.wordpress.com/2012/12/20/timebroker-kills-the-metromodern-ui/
- Press the shortcut combination: Windows key + R, type in “cmd” and click OK.
- In the command window, type in “regedit” and hit enter
- Search and navigate to the registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TimeBroker - Modify the “Start” value to “4″ (4 for disabled; 3 for manual).
- Reboot the system and the Start Screen should work normally for you to uninstall Apps.
You may need to manually stop TimeBroker again having rebooted as it has a nasty Dracula habit of rising from the grave!