I have tried to use
res/layout/my_layout.xml // layout for normal screen size ("default")
res/layout-small/my_layout.xml // layout for small screen size
res/layout-large/my_layout.xml // layout for large screen size
res/layout-xlarge/my_layout.xml // layout for extra large screen size
res/layout-xlarge-land/my_layout.xml // layout for extra large in landscape
When i launch my app it is able to see the res/layout-xlarge/my_layout.xml but when I turn the orientation (the view does turn), it doesn’t show the res/layout-xlarge-land/my_layout.xml but the portrait one instead. (sorry for my bad english)
Not all orientations are supported in all versions of the SDK. I could not find the information saying what SDK version xlarge-land is available in but I would bet if you change your minimum SDK version to 16 and target building to 16 it will work. Try going from there and see if you can find when it stops working.
Related: http://developer.android.com/guide/topics/resources/providing-resources.html#Compatibility