Setting space preference with panel wizard does not work

I like to set the presentation preference on a space to use left-column. After trying that in both the following release, I couldn't get that to work.

xwiki enterprise 1.4-milestone-1.8982 [ standalone installation]
xwiki enterprise 1.5-M2 [ tomcat / mysql ]

I was trying to set the preference for Main.

On 1.4, Administration->space preference->presentation uses a drop-down [yes|no values] for showing either left or right column. But that only works for the right column, no effect on the right.

On 1.5, the Panel Wizard ->page layout tab makes that config looks very easy. But again it does not work. Selecting either left or right column would display a positive confirmation popup. But when viewing a page in that space, it's reverted to NoSideColumn. Revisiting the panel layout tab confirms it.