When Favourites are redirected and a user attempts to View or Add favourites within IE the user is presented with a greyed out box as bellow
This can be seen in two scenarios
1) Favourites have been redirected, but the location added to the redirected is a mapped drive.
2) The location you have specified is not a mapped drive but the user does not have permission to the specified location in the redirect.
It recommended to only set redirection to a UNC path or utilize environment variables to a UNC path. Further information on this can be found in the following Microsoft link.