Hi,
According to your description, it seems to be caused by "protected mode".
Note: In the Windows 8 Release Preview, if you enable Protected Mode for the Local Intranet and Trusted Zones, even if you enable EPM, the Intranet and Trusted Zones will run in 32bit LowIL rather than a 64bit AppContainer.
For more information, you can refer the blog:
#Understanding Enhanced Protected Mode
http://blogs.msdn.com/b/ieinternals/archive/2012/03/23/understanding-ie10-enhanced-protected-mode-network-security-addons-cookies-metro-desktop.aspx
Hope it can help you.
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