can't use overlay with prosper layout

[Nicolas Roy]

Hej

When i use the slide (prosper) layout, the overlay doesn't seem to work.
I get the following error message:

\overlay can only be used in slide environments
\lyxnewoverlay{page2}

I have Lyx 1.3.2 and the prosper layout downloaded from 
http://www.md.kth.se/~chr/lyx/examples/prosper/layouts/prosper.layout

Thanks for help.
Nicolas Roy