Here is a quick-fix for an unsettling error message.  The error message is:

An IIS directory entry couldn’t be created. The error message is Access is denied.
. HResult = -2147024891
+ CategoryInfo : NotInstalled: (MB2Exchange (Default Web Site):ADObjectId) [Get-OwaVirtualDirectory], II
+ FullyQualifiedErrorId : 401839E9,Microsoft.Exchange.Management.SystemConfigurationTasks.GetOwaVirtualDirectory

This error pops up when attempting to view the properties of the OWA or ActiveSync tabs within the Exchange 2010 Management Console, and only in a mixed Exchange 2007-2010 environment.  The fix is to add the group Exchange Trusted Subsystem to the local administrators group on the Exchange 2007 server.